Modify the built-in text search parser to handle URLs more nearly according

Modify the built-in text search parser to handle URLs more nearly according
to RFC 3986.  In particular, these characters now terminate the path part
of a URL: '"', '<', '>', '\', '^', '`', '{', '|', '}'.  The previous behavior
was inconsistent and depended on whether a "?" was present in the path.
Per gripe from Donald Fraser and spec research by Kevin Grittner.

This is a pre-existing bug, but not back-patching since the risks of
breaking existing applications seem to outweigh the benefits.