FreeBSD stores INT_MIN and INT_MAX in sys/limits.h only. Other systems
(Solaris) have it in sys/types.h and do not have sys/limits.h. Let's
include sys/limits.h only if INT_MAX is not defined.
Sorin Pop reported a patch to fix build on FreeBSD.
The file common/standard.h used an fd_set in a declaration
but did not include enough headers for it to be known.