Explicitly test for broken strnvis.

NetBSD added an strnvis and unfortunately made it incompatible with the
existing one in OpenBSD and Linux's libbsd (the former having existed
for over ten years). Despite this incompatibility being reported during
development (see http://gnats.netbsd.org/44977) they still shipped it.
Even more unfortunately FreeBSD and later MacOS picked up this incompatible
implementation.  Try to detect this mess, and assume the only safe option
if we're cross compiling.

OpenBSD 2.9 (2001): strnvis(char *dst, const char *src, size_t dlen, int flag);
NetBSD 6.0 (2012):  strnvis(char *dst, size_t dlen, const char *src, int flag);

ok djm@
1 file changed
tree: 91a179e60ae8cc35786a901fd2f79c00f6e2ad46
  1. .skipped-commit-ids
  2. CREDITS
  3. INSTALL
  4. LICENCE
  5. Makefile.in
  6. OVERVIEW
  7. PROTOCOL
  8. PROTOCOL.agent
  9. PROTOCOL.certkeys
  10. PROTOCOL.chacha20poly1305
  11. PROTOCOL.key
  12. PROTOCOL.krl
  13. PROTOCOL.mux
  14. README
  15. README.dns
  16. README.platform
  17. README.privsep
  18. README.tun
  19. TODO
  20. aclocal.m4
  21. addrmatch.c
  22. atomicio.c
  23. atomicio.h
  24. audit-bsm.c
  25. audit-linux.c
  26. audit.c
  27. audit.h
  28. auth-bsdauth.c
  29. auth-chall.c
  30. auth-krb5.c
  31. auth-options.c
  32. auth-options.h
  33. auth-pam.c
  34. auth-pam.h
  35. auth-passwd.c
  36. auth-rh-rsa.c
  37. auth-rhosts.c
  38. auth-rsa.c
  39. auth-shadow.c
  40. auth-sia.c
  41. auth-sia.h
  42. auth-skey.c
  43. auth.c
  44. auth.h
  45. auth1.c
  46. auth2-chall.c
  47. auth2-gss.c
  48. auth2-hostbased.c
  49. auth2-kbdint.c
  50. auth2-none.c
  51. auth2-passwd.c
  52. auth2-pubkey.c
  53. auth2.c
  54. authfd.c
  55. authfd.h
  56. authfile.c
  57. authfile.h
  58. bitmap.c
  59. bitmap.h
  60. blocks.c
  61. bufaux.c
  62. bufbn.c
  63. bufec.c
  64. buffer.c
  65. buffer.h
  66. buildpkg.sh.in
  67. canohost.c
  68. canohost.h
  69. chacha.c
  70. chacha.h
  71. channels.c
  72. channels.h
  73. cipher-3des1.c
  74. cipher-aes.c
  75. cipher-aesctr.c
  76. cipher-aesctr.h
  77. cipher-bf1.c
  78. cipher-chachapoly.c
  79. cipher-chachapoly.h
  80. cipher-ctr.c
  81. cipher.c
  82. cipher.h
  83. cleanup.c
  84. clientloop.c
  85. clientloop.h
  86. compat.c
  87. compat.h
  88. config.guess
  89. config.sub
  90. configure.ac
  91. contrib/
  92. crc32.c
  93. crc32.h
  94. crypto_api.h
  95. deattack.c
  96. deattack.h
  97. defines.h
  98. dh.c
  99. dh.h
  100. digest-libc.c
  101. digest-openssl.c
  102. digest.h
  103. dispatch.c
  104. dispatch.h
  105. dns.c
  106. dns.h
  107. ed25519.c
  108. entropy.c
  109. entropy.h
  110. fatal.c
  111. fe25519.c
  112. fe25519.h
  113. fixalgorithms
  114. fixpaths
  115. fixprogs
  116. ge25519.c
  117. ge25519.h
  118. ge25519_base.data
  119. groupaccess.c
  120. groupaccess.h
  121. gss-genr.c
  122. gss-serv-krb5.c
  123. gss-serv.c
  124. hash.c
  125. hmac.c
  126. hmac.h
  127. hostfile.c
  128. hostfile.h
  129. includes.h
  130. install-sh
  131. kex.c
  132. kex.h
  133. kexc25519.c
  134. kexc25519c.c
  135. kexc25519s.c
  136. kexdh.c
  137. kexdhc.c
  138. kexdhs.c
  139. kexecdh.c
  140. kexecdhc.c
  141. kexecdhs.c
  142. kexgex.c
  143. kexgexc.c
  144. kexgexs.c
  145. key.c
  146. key.h
  147. krl.c
  148. krl.h
  149. log.c
  150. log.h
  151. loginrec.c
  152. loginrec.h
  153. logintest.c
  154. mac.c
  155. mac.h
  156. match.c
  157. match.h
  158. md-sha256.c
  159. md5crypt.c
  160. md5crypt.h
  161. mdoc2man.awk
  162. misc.c
  163. misc.h
  164. mkinstalldirs
  165. moduli
  166. moduli.5
  167. moduli.c
  168. monitor.c
  169. monitor.h
  170. monitor_fdpass.c
  171. monitor_fdpass.h
  172. monitor_mm.c
  173. monitor_mm.h
  174. monitor_wrap.c
  175. monitor_wrap.h
  176. msg.c
  177. msg.h
  178. mux.c
  179. myproposal.h
  180. nchan.c
  181. nchan.ms
  182. nchan2.ms
  183. opacket.c
  184. opacket.h
  185. openbsd-compat/
  186. openssh.xml.in
  187. opensshd.init.in
  188. packet.c
  189. packet.h
  190. pathnames.h
  191. pkcs11.h
  192. platform-pledge.c
  193. platform-tracing.c
  194. platform.c
  195. platform.h
  196. poly1305.c
  197. poly1305.h
  198. progressmeter.c
  199. progressmeter.h
  200. readconf.c
  201. readconf.h
  202. readpass.c
  203. regress/
  204. rijndael.c
  205. rijndael.h
  206. rsa.c
  207. rsa.h
  208. sandbox-capsicum.c
  209. sandbox-darwin.c
  210. sandbox-null.c
  211. sandbox-pledge.c
  212. sandbox-rlimit.c
  213. sandbox-seccomp-filter.c
  214. sandbox-solaris.c
  215. sandbox-systrace.c
  216. sc25519.c
  217. sc25519.h
  218. scp.1
  219. scp.c
  220. servconf.c
  221. servconf.h
  222. serverloop.c
  223. serverloop.h
  224. session.c
  225. session.h
  226. sftp-client.c
  227. sftp-client.h
  228. sftp-common.c
  229. sftp-common.h
  230. sftp-glob.c
  231. sftp-server-main.c
  232. sftp-server.8
  233. sftp-server.c
  234. sftp.1
  235. sftp.c
  236. sftp.h
  237. smult_curve25519_ref.c
  238. ssh-add.1
  239. ssh-add.c
  240. ssh-agent.1
  241. ssh-agent.c
  242. ssh-dss.c
  243. ssh-ecdsa.c
  244. ssh-ed25519.c
  245. ssh-gss.h
  246. ssh-keygen.1
  247. ssh-keygen.c
  248. ssh-keyscan.1
  249. ssh-keyscan.c
  250. ssh-keysign.8
  251. ssh-keysign.c
  252. ssh-pkcs11-client.c
  253. ssh-pkcs11-helper.8
  254. ssh-pkcs11-helper.c
  255. ssh-pkcs11.c
  256. ssh-pkcs11.h
  257. ssh-rsa.c
  258. ssh-sandbox.h
  259. ssh.1
  260. ssh.c
  261. ssh.h
  262. ssh1.h
  263. ssh2.h
  264. ssh_api.c
  265. ssh_api.h
  266. ssh_config
  267. ssh_config.5
  268. sshbuf-getput-basic.c
  269. sshbuf-getput-crypto.c
  270. sshbuf-misc.c
  271. sshbuf.c
  272. sshbuf.h
  273. sshconnect.c
  274. sshconnect.h
  275. sshconnect1.c
  276. sshconnect2.c
  277. sshd.8
  278. sshd.c
  279. sshd_config
  280. sshd_config.5
  281. ssherr.c
  282. ssherr.h
  283. sshkey.c
  284. sshkey.h
  285. sshlogin.c
  286. sshlogin.h
  287. sshpty.c
  288. sshpty.h
  289. sshtty.c
  290. survey.sh.in
  291. ttymodes.c
  292. ttymodes.h
  293. uidswap.c
  294. uidswap.h
  295. umac.c
  296. umac.h
  297. utf8.c
  298. utf8.h
  299. uuencode.c
  300. uuencode.h
  301. verify.c
  302. version.h
  303. xmalloc.c
  304. xmalloc.h