Add "least", "fast" and "max" C fixed-width types

[PhilipRoman]

Changes

This PR adds support for the remaining C99/C++11 fixed-width types:

int_fast8_t
int_fast16_t
int_fast32_t
int_fast64_t

int_least8_t
int_least16_t
int_least32_t
int_least64_t

uint_fast8_t
uint_fast16_t
uint_fast32_t
uint_fast64_t

uint_least8_t
uint_least16_t
uint_least32_t
uint_least64_t

intmax_t
uintmax_t

I have tested the changes with nano as well as other regex testing tools.

I didn't add the respective versions for u_int... because I couldn't find reliable sources on this topic.

[scopatz]

Thanks!