Fortran: Follow fixes to -freal-{4,8}-real* handling [PR99355,PR57871]

Fortran: Follow fixes to -freal-{4,8}-real* handling [PR99355,PR57871]

gcc/fortran/ChangeLog:

	PR fortran/99355
	PR fortran/57871
	* invoke.texi (-freal{4,8}-real-*): Extend description.
	* primary.c (match_real_constant): Also promote real literals
	with '_kind' number.

gcc/testsuite/ChangeLog:

	* gfortran.dg/real4-10-real8-10.f90: Add check for real literals
	with '_kind' number.
	* gfortran.dg/real4-10-real8-16.f90: Likewise.
	* gfortran.dg/real4-10-real8-4.f90: Likewise.
	* gfortran.dg/real4-10.f90: Likewise.
	* gfortran.dg/real4-16-real8-10.f90: Likewise.
	* gfortran.dg/real4-16-real8-16.f90: Likewise.
	* gfortran.dg/real4-16-real8-4.f90: Likewise.
	* gfortran.dg/real4-16.f90: Likewise.
	* gfortran.dg/real4-8-real8-10.f90: Likewise.
	* gfortran.dg/real4-8-real8-16.f90: Likewise.
	* gfortran.dg/real4-8-real8-4.f90: Likewise.
	* gfortran.dg/real4-8.f90: Likewise.
	* gfortran.dg/real8-10.f90: Likewise.
	* gfortran.dg/real8-16.f90: Likewise.
	* gfortran.dg/real8-4.f90: Likewise.