Add no-FPU ColdFire math_private.h.

Add no-FPU ColdFire math_private.h.

As with some other soft-float configurations, no-FPU ColdFire needs
various fenv.h functions and glibc-internal macros overridden in
math_private.h to avoid references to undefined FE_* macros when
building glibc.  This patch adds a suitable math_private.h, based on
the MicroBlaze one (Nios II and Tile also have similar files).

There's a case for having such a file in sysdeps/ieee754/soft-fp so
this logic is applied more generally to configurations without
exceptions and rounding modes, even when the relevant macros are
defined in fenv.h - the only case where that might be inappropriate is
ARM soft-float (where the fenv.h functions might or might not work at
runtime, depending on whether the processor used at runtime supports
VFP).  There's also a case that soft-float configurations (on
processors with both hard-float and soft-float) should more
consistently avoid defining FE_* macros in bits/fenv.h when not
actually supported.  But both of those are separate potential
cleanups.

This allows the no-FPU ColdFire build to get further (another fix is
needed to allow the build to complete).

	* sysdeps/m68k/coldfire/nofpu/math_private.h: New file.  Based on
	MicroBlaze file.