Provide an alternate interface to the arena allocator to avoid wasting time on unnecessary calls to memset()

Rationale: "Basic allocation" refers to things outside of parsing proper,
mostly initialization. If such allocations fail, the system is globally
emory-starved from which it will likely not recover by returning failure.
In this case, terminating the process is in fact the most robust strategy as
it may mean the difference between a permanent hang and a temporary crash.

They apparently removed alloc_size at some point (it was a no-op
beforehand), causing the attribute to throw an error when clang compiles
anything including allocator.h.

Import combinator and allocator APIs into SWIG. Next is glue. Need to fix unions in HParsedToken and HCaseResult.

Import combinator and allocator APIs into SWIG. Next is glue. Need to fix unions in HParsedToken and HCaseResult.

Import combinator and allocator APIs into SWIG. Next is glue. Need to fix unions in HParsedToken and HCaseResult.