Fortran: degree trigonometric functions and procedure pointers [PR121366]

While libgfortran already provides an implementation of the degree
trigonometric functions and their inverses with argument passed by value,
some situations (e.g. when used as procedure pointer target) need the
variant with Fortran calling conventions where the argument is passed by
reference.  Provide the appropriate specific wrappers.

	PR fortran/121366

gcc/fortran/ChangeLog:

	* intrinsic.texi: Remove documentation of GNU intrinsic extensions
	(CCOSD,ZCOSD,CDCOSD) that were never implemented.
	* iresolve.cc (gfc_resolve_trig): Fix resolution of degree
	trigonometric functions and generate references to the proper
	library functions.
	(gfc_resolve_trig2): Likewise.
	* trans-decl.cc (gfc_get_extern_function_decl): Ensure that isym
	is set when resolving intrinsic procedures.

libgfortran/ChangeLog:

	* Makefile.am: Add dependency on wrappers to degree trigonometric
	functions.
	* Makefile.in: Regenerate.
	* gfortran.map: Add references to new wrapper functions.
	* intrinsics/trigd_specific.F90: New file.

gcc/testsuite/ChangeLog:

	* gfortran.dg/trigd_1.f90: New test.