mpx_set_str2(mpx_t, const char*, const char*, int) suggestion

[Pierre Chatelier]

Hello,

Currently the various mpx structures (mpz_t, mpq_t, mpf_t) have an output function similar to :
mpx_set_str(mpx_t r, const char *sp, int base)

For the sake of performance, I suggest a new prototype mpx_set_str2(mpx_t r, const char *start, const char* end, int base) (where [start;end[ is the string to consider)
For me, the interest is :
	-I looked at the current implementation of mpz_t. It seems very easy to change
	-It saves a call to strlen() in the current implementation
	-users of gmplib do not need to create intermediate strings with '\0' terminator when parsing substring from complex input data

If necessary, I can submit a patch, but what do you think at first sight ?

Regards,

Pierre Chatelier