Protect the trigd functions in libgfortran from unavailable math functions.

Protect the trigd functions in libgfortran from unavailable math functions.

libgfortran/ChangeLog:

2020-04-22  Fritz Reese  <foreese@gcc.gnu.org>

	PR libfortran/94694
	PR libfortran/94586
	* intrinsics/trigd.c, intrinsics/trigd_lib.inc, intrinsics/trigd.inc:
	Guard against unavailable math functions.
	Use suffixes from kinds.h based on the REAL kind.

gcc/fortran/ChangeLog:

2020-04-22  Fritz Reese  <foreese@gcc.gnu.org>

	* trigd_fe.inc: Use mpfr to compute cosd(30) rather than a host-
	precision floating point literal based on an invalid macro.