* libgfortran.h (support_fpu_underflow_control,
        get_fpu_underflow_mode, set_fpu_underflow_mode): New prototypes.
	* config/fpu-*.h (support_fpu_underflow_control,
	get_fpu_underflow_mode, set_fpu_underflow_mode):
	New functions.
	* ieee/ieee_arithmetic.F90: Support underflow control.

	* gfortran.dg/ieee/underflow_1.f90: New file.

From-SVN: r212407