Add more QQFieldElem and ZZRingElem ccalls (#1866)

- add some missing add!, mul!, etc. methods
- add more efficient +, -, * methods for a ZZRingElem or QQFieldElem
  as first argument, and an integer as second argument
- optimize is_one and is_zero for QQFieldElem
- drop some pointless uses of `@inline`
- add `cmp` for QQFieldElem and use it
- add numerator! and denominator!
- change a bunch of "unsafe" methods to accept ZZRingElemOrPtr resp.
  QQFieldElemOrPtr instead of just ZZRingElem and QQFieldElem to
  make them more flexible
---------

Co-authored-by: Lars Göttgens <lars.goettgens@gmail.com>

src/Exports.jl

@@ -137,6 +137,7 @@ export degree_fmpz
 export degrees
 export degrees_fit_int
 export degrees_fmpz
+#export denominator!  # not exported for now to avoid clash with Hecke
 export derivative
 export det
 export det_divisor
@@ -464,6 +465,7 @@ export nullspace_right_rational
 export number_field
 export number_of_partitions
 export numpart
+#export numerator!  # not exported for now to avoid clash with Hecke
 export oct
 export one
 export one!