src/lib/cap.c: fix build with older userspace

When building on RHEL5, the following error appears:

> cap.c: In function 'set_cap_bound':
> cap.c:213: error: 'PR_CAPBSET_DROP' undeclared (first use in this function)
> cap.c:213: error: (Each undeclared identifier is reported only once
> cap.c:213: error: for each function it appears in.)

Fix as usual.

Signed-off-by: Kir Kolyshkin <kir@openvz.org>
1 file changed