precisely what they need, and actually control the format of the
resulting name or description

spike branch: parsing of more complex backend requested parameters
string, with optional paramaters, etc. formatting of code fixed, unused
string based parsing of request parameters removed, etc.

right now there is duplication as the enum backend value is still
present- need to find out if it's OK to make a breaking change for
anyone who is for reasons known only to themselves chekcing which
backend enum value is one a parser they may have created and compiled...

compared to with strnig functions. WIP, feedback requested

committing now because of harddrive making a bad sound again.

hard drive sounded bad. TODO includes free and copy updated and a bunch
of refactoring / redesign of the solution

"glr(1)" and call compile for the appropriate backend. Needs clean up
and refactor, and tests, but it compiles and my hard-drive is
periodically making threatening noises...

the regex backend already returned 2 for an internal failure, contrary to
documentation, so this mainly brings the latter in line with existing behavior.

at the same time, fix a bug: h_compile would previously return "false" (0) on
exceptions (longjmp).

make use of our new freedom to signal different error conditions from the
context-free backends, notably "incompatible combinator" vs. "unresolvable
conflict".

Refactored all of the desugaring code to no longer depend on memory being initialized to 0. Everything is about 12% faster now.