Make parsers `foo__m` macros that expand to `foo__m(mm__, ...)`

[pesco]

This is an idea for a possible enhancement. Feedback welcome!

For the default case, a user would globally declare mm__ = &h_system_allocator. In combinators, the standard argument would shadow the global variable.

Benefits:

• (Motivation:) In an allocator-specific function, shadowing the global ensures that the user cannot use it. This is important in the h_bind combinator I made for DNP3: It typically allocates continuation parsers on every call during the parse and one missed allocation makes a memory leak.
• Allocator-specific code remains as readable as code using the default allocator.

Cons:

• User has to add one boilerplate delaration in the typical case.
• Does this generate trouble for bindings?
• Danger of mistyping the standard argument and defaulting to the global.