Add ColdFire math-tests.h.

Since I've been fixing build issues for ColdFire, this patch adds a
math-tests.h file for ColdFire, reflecting the lack of support for
exceptions and rounding modes for soft float.  I think it is logically
correct, but have not tested it beyond build-many-glibcs.py for both
hard and soft float.

	* sysdeps/m68k/coldfire/math-tests.h: New file.