Macroize inclusion of math-finite.h

This patch macroizes the declarations in math/bits/math-finite.h
similarly to what math/bits/mathcalls.h does.  For each floating-point
type, the file is included once in math/math.h.  This will reduce the
amount of repetitive boilerplate required when adding float128
versions of these declarations.

Tested for powerpc64le and s390x.

	* math/math.h: Include bits/math-finite.h once per
	floating-point type.
	* math/bits/math-finite.h: Macroize all declarations by
	floating-point type.