Replaced existing code for If-Modified-Since, If-Unmodified-Since,

If-Match, and If-None-Match in order to correct the order of preference
regarding ETags and to make use of the parseHTTPdate routine.  Also
modified the comparison for last-modification time so that it changes
Last-Modified only if it is greater than the current time, rather than
the request_time. We also now check to be sure that the incoming
If-Modified-Since value is not greater than the request_time, which was
the last non-compliant bit for HTTP/1.1.

Finally, I updated the Makefile dependency list, since it was woefully
out-of-date and hard to read in its prior form.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@76967 13f79535-47bb-0310-9956-ffa450edef68