Testing len > 0 is redundant when *field is a "\0" and mismatches here,
folded flag was a no-op, unused once we added continue; logic.
Fix these as initially attempted in r1755114.

Add some comments to make this code slightly more legible to the reviewer.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1755125 13f79535-47bb-0310-9956-ffa450edef68