Fortran: Use mpfr_sinu etc. with mpfr 4.2.0+ for degree trigonometric functions ...

Fortran: Use mpfr_sinu etc. with mpfr 4.2.0+ for degree trigonometric functions [PR120225]

As MPFR 4.2.0 added, support for degree trigonometric functions by via the
mpfr_...u functions (for u = 360), it makes sense to use them if available.
If MPFR is older, the current implementation is used as fallback.

	PR fortran/120225

gcc/fortran/ChangeLog:

	* simplify.cc: Include "trigd_fe.inc" only with MPFR < 4.2.0.
	(rad2deg, rad2deg): Only define if MPFR < 4.2.0.
	(gfc_simplify_acosd, gfc_simplify_asind, gfc_simplify_atand,
	gfc_simplify_atan2d, gfc_simplify_cosd, gfc_simplify_tand,
	gfc_simplify_cotand): Use mpfr_...u functions with MPFR >= 4.2.0.