fix mpfr(str, prec, base) precision bug
mpfr python long math tests and related bugfixes
mpfr python long comparison tests and related bugfixe
add invalid type math/cmp tests
mpfr invalid init tests
add mpfr division by zero tests
remove mpfr.__ceil__, mpfr.__floor__ since they use float
mpfr.__int__ special value tests
mpfr.__int__ bigint fix
x ** mpq returning mpfr