Performance fix for ap_ssi_get_tag_and_value: do a lightweight

scan through the tag value until/unless we reach a backslash
that necessitates the more complicated scanner loop.  In cases
where there isn't a backslash in the tag value, this reduces
the overhead of the scan from 5 comparisons per character to 3.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93983 13f79535-47bb-0310-9956-ffa450edef68