allocation functions

[Paul Zimmermann]

It seems to me that the interface to allocation functions is not complete:

1) the functions allocate_function, reallocate_function, deallocate_function
   from the manual are not in gmp.h. Are those only fake functions?

2) when using mpz_get_str, the returned string is allocated using the current
   gmp allocation function, so one would like to free it using the current
   gmp free function, but there it is not documented (see 1).

3) a function mp_reset_memory_functions() would be nice, that would reset
   to the default functions

Paul