Bundle helpers for url_rewrite

Bundle helpers for url_rewrite

Adds the --enable-url-rewrite-helpers configure time option.
see release notes or ./configure help text.

Bundles two 'fake' helpers with exemplar code for shell and C++ coding:

 url_fake_rewrite
	- C++ helper with old non-concurrent protocol.

 url-fake-rewrite.sh
	- shell helper with concurrent and non-concurrent protocols.

Also, some polishing is done to debug code for helpers.