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.

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...

that we also check to confirm both engines have consume the same number
of tokens (and thus have actually both arrived at the same state for the
same partial input stream)

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".