Rename int_*() functions to *_int()

Rename int_*() functions to *_int()

There is a preference for suffixes to indicate that a function is internal
rather than prefixes. Note: the suffix is only required to disambiguate
internal functions and public symbols with the same name (but different
case)

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>