Problems exposed by Sunpro C/Solaris 11.

 * Needs its own errloc_re.
 * Conformance switches were too aggressive.
 * Use syntax-check-only mode.
 * decltests/limits.ini: Give all the integer range constants their
   accurate type.
 * prereqs.ini: resolv.h may require time.h; netinet/ip_icmp.h may require
   netinet/in.h.
 * single_test.py: Yet more adjustment of the conflict detector.