cleanup RewriteCond evaluation.

- avoid unnecessary memory operations
- parse non-regex patterns at configuration time, which
- gives the ability to throw a useful warning, where [NC] is not supported
- and speeds up processing at runtime
- allow [NC] for simple comparison pattern (=)
- improve readability


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@100862 13f79535-47bb-0310-9956-ffa450edef68