fortran: add constant input support for trig functions with half-revolutions

fortran: add constant input support for trig functions with half-revolutions

This patch introduces constant input support for trigonometric functions,
including those involving half-revolutions. Both valid and invalid inputs have
been thoroughly tested, as have mpfr versions greater than or equal to 4.2 and
less than 4.2.

Inspired by Steve's previous work, this patch also fixes subtle bugs revealed
by newly added test cases.

If this patch is merged, I plan to work on middle-end optimization support for
previously added GCC built-ins and libgfortran intrinsics.

	PR fortran/113152

gcc/fortran/ChangeLog:

	* gfortran.h (enum gfc_isym_id): Add new enum.
	* intrinsic.cc (add_functions): Register new intrinsics. Changing the call
	from gfc_resolve_trigd{,2} to gfc_resolve_trig{,2}.
	* intrinsic.h (gfc_simplify_acospi, gfc_simplify_asinpi,
	gfc_simplify_asinpi, gfc_simplify_atanpi, gfc_simplify_atan2pi,
	gfc_simplify_cospi, gfc_simplify_sinpi, gfc_simplify_tanpi): New.
	(gfc_resolve_trig): Rename from gfc_resolve_trigd.
	(gfc_resolve_trig2): Rename from gfc_resolve_trigd2.
	* iresolve.cc (gfc_resolve_trig): Rename from gfc_resolve_trigd.
	(gfc_resolve_trig2): Rename from gfc_resolve_trigd2.
	* mathbuiltins.def: Add 7 new math builtins and re-align.
	* simplify.cc (gfc_simplify_acos, gfc_simplify_asin,
	gfc_simplify_acosd, gfc_simplify_asind): Revise error message.
	(gfc_simplify_acospi, gfc_simplify_asinpi,
	gfc_simplify_asinpi, gfc_simplify_atanpi, gfc_simplify_atan2pi,
	gfc_simplify_cospi, gfc_simplify_sinpi, gfc_simplify_tanpi): New.

gcc/testsuite/ChangeLog:

	* gfortran.dg/dec_math_3.f90: Test invalid input.
	* gfortran.dg/dec_math_5.f90: Test valid output.
	* gfortran.dg/dec_math_6.f90: New test.

Signed-off-by: Yuao Ma <c8ef@outlook.com>
Co-authored-by: Steven G. Kargl <kargl@gcc.gnu.org>