Introduce ap_scan_http_token / ap_scan_http_field_content for a much

more efficient pass through the header text; rather than reparsing
the strings over and over under the HTTP_CONFORMANCE_STRICT fules.

Improve logic and legibility by eliminating multiple repetitive tests
of the STRICT flag, and simply reorder 'classic' behavior first and
this new parser second to simplify the diff. Because of the whitespace
change (which I had wished to dodge), reading this --ignore-all-space
is a whole lot easier. Particularly against 2.4.x branch, which is now
identical in the 'classic' logic flow. Both of which I'll share with dev@



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1754556 13f79535-47bb-0310-9956-ffa450edef68