ping: fix -Wformat-truncating warning with GCC

Increase buffer size for the string representation of n_time

ICMP timestamp is a 32-bit number. In pr_ntime(), number of minutes
and seconds is always 2 characters wide. Max. number of hours is 4
characters wide. The buffer size should be at least:

4 + 2 + 2 + 1 (':') + 1 (':') + 1 ('\0') = 11

Import from FreeBSD base revision 351223
1 file changed
tree: 11c9c17661d69d9f7cd21c997b6960c88cc2f918
  1. build.sh
  2. linux-sysctl/
  3. ping.8
  4. ping.c