* rewriting fixes:
server side: cookie rewriting: if httponly cookie with mp_/if_ modifier and path ends with '/', add set-cookie for all known modifiers
content length parsing: improve content-length parsing to support 'content-length: num,num', parse out the first number (occasionally seen with range requests when range is dropped for upstream)
wombat: rewrite_elem: use element.ownerDocument for resolving baseUri for parent paths
tests: add tests for cookie all modifier rewrite, bad content-length parsing (skip for py2.7)