*) core: Drop an invalid Last-Modified header value coming

  *) core: Drop an invalid Last-Modified header value coming
     from a (F)CGI script instead of replacing it with Unix epoch.
     Warn the users about Last-Modified header value replacements
     and violations of the RFC.
     trunk patch: http://svn.apache.org/r1748379
                  http://svn.apache.org/r1750747
                  http://svn.apache.org/r1750749
                  http://svn.apache.org/r1750953
                  http://svn.apache.org/r1751138
                  http://svn.apache.org/r1751139
                  http://svn.apache.org/r1751147
                  http://svn.apache.org/r1757818
                  http://svn.apache.org/r1879253
                  http://svn.apache.org/r1879348
     2.4.x: trunk patches work, final view:
            http://home.apache.org/~elukey/httpd-2.4.x-core-last_modified_tz_logging.patch
            svn merge -c 1748379,1750747,1750749,1750953,1751138,1751139,1751139,1757818,1879253,r1879348 ^/httpd/httpd/trunk .
     The code has been tested with a simple PHP script returning different Last-Modified
     headers (GMT now, GMT now Europe/Paris, GMT tomorrow, GMT yesterday, PST now).
     +1: elukey, jorton, jim
     jorton: +1 though I'd say log at WARN or INFO for the APR_BAD_DATE case
             rather than "silently" (at normal log-level) dropping the parsed header?
             [also nit: wrapping a lone ap_log_rerror(,APLOG_X) call in
             if (APLOGrX(..) is unnecessary/redundant]

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1879641 13f79535-47bb-0310-9956-ffa450edef68