Rationale: If memory allocation fails in the inner parse and we
longjump up the stack, the temporary arena will be missed and leak.

NB: This change means that any allocations done by the continuation
(in the form of new parsers, probably) will persist for the
lifetime of the parse result. Beware of wasting too much memory
this way! The bind continuation should generally keep dynamic
allocations to a minimum.

fix LIBPATH order for building test_suite

Don't try to recall() primitive results

fix --coverage build option; building with it now creates .gcda files…

Don't create dummy LR-cache entries for parsers that will never recurse

add platform.h to distribution headers

Allocate 256 bits, not 256 bytes, for a charset

Fix charset conflicts

Report correct token position from LR backends

Iterative (chunked) input processing