re PR fortran/82143 (add a -fdefault-real-16 flag)

re PR fortran/82143 (add a -fdefault-real-16 flag)

2017-09-26  Janus Weil  <janus@gcc.gnu.org>

	PR fortran/82143
	PR fortran/82324
	* doc/sourcebuild.texi: Document fortran_real_10 and fortran_real_16.

2017-09-26  Janus Weil  <janus@gcc.gnu.org>

	PR fortran/82143
	PR fortran/82324
	* lib/target-supports.exp (check_effective_target_fortran_real_10): New.
	* gfortran.dg/promotion_3.f90: Only run if real(16) is available.
	* gfortran.dg/promotion_4.f90: Only run if real(10) is available.
	Don't assume that DOUBLE PRECISION has kind=16.

From-SVN: r253214