Allow anytoa() to (optionally) take just one (Math::MPFR object) arg, instead of the two args originally mandated.
Simplify Makefile.PL.
Replace XS defines NV_IS_FLOAT128 and NV_IS_LONG_DOUBLE with USE_QUADMATH and USE_LONG_DOUBLE (which are already defined by perl headers).
Replace XS defines NV_IS_DOUBLE and NV_IS_53_BIT with the condition NVSIZE == 8 (which is already defined in the perl headers).
Add Rmpfr_set_IV.
Utilize Rmpfr_cmp_IV and Rmpfr_cmp_NV in the overloaded comparison subs.
Remove the *_UV functions and adapt the corresponding *_IV functions to handle the case that SvUOK() is true. (This is how it should always have been.)
Add Rmpfr_init_set_IV, Rmpfr_init_set_NV and Rmpfr_init_set_float128.
Add Rmpfr_cmp_float128.
Rmpfr_cmp_IV, Rmpfr_set_IV, Rmpfr_init_set_IV, Rmpfr_cmp_NV, Rmpfr_set_NV and Rmpfr_init_set_NV accept only scalars that are IOK or (respectively) NOK as their 2nd argument.