Support of Stateful Allocators in spirit

[evilissimo@…]

Currently it's not possible to avoid allocations from happening with the standard allocators of the used standard library.

That makes it quite impossible to manage the memory for the parser.

Some use case examples:

• Writing a library in C++ with a C interface allowing the user to pass 'malloc' and 'free' replacements.
• Writing a program that uses a pool memory allocator

I know that this probably won't be too high on your todo list, however it'd be great to have.

[evilissimo@…]

A potential solution to support allocators on rule and grammar