Remove _Mlong_double_ etc. macros.

Remove _Mlong_double_ etc. macros.

math.h has a macro _Mlong_double_ for the type to use when declaring
long double functions, and similar macros for other types.
math/Makefile uses -D_Mlong_double_=double in the case of long double
having the same ABI as double.

This originates with:

Mon Jul  8 13:37:40 1996  Roland McGrath  <roland@delasyd.gnu.ai.mit.edu>

        * math/math.h (_Mfloat_, _Mlong_double_): New macros, defined iff not
        already defined to float, long double.  Use those macros for _Mdouble_
        defns when including mathcalls.h.
        * math/Makefile [$(long-double-fcts) != yes] (CPPFLAGS): Append
        -D_Mlong_double_=double.

However, math.h stopped declaring long double functions in the case of
long double having the same ABI as double (and thus probably stopped
actually needing the Makefile definition of _Mlong_double_) with:

1998-11-05  Ulrich Drepper  <drepper@cygnus.com>

        * math/math.h: Unconditionally include bits/mathdef.h.  Declare
        long double functions only if __NO_LONG_DOUBLE_MATH is not
        defined.
        * sysdeps/generic/bits/mathdef.h: Define only if __USE_ISOC9X.
        Define __NO_LONG_DOUBLE_MATH.
        * sysdeps/m68k/fpu/bits/mathdef.h: Define only if __USE_ISOC9X.
        * sysdeps/i386/fpu/bits/mathdef.h: Likewise.

The declarations were since restored for compiling user code, but
remain absent when _LIBC is defined, which is sufficient to avoid
problems declaring function aliases of incompatible types.  Thus the
indirection through the _Mlong_double_ macro is not needed (probably
since that 1998 patch), and this patch removes _Mlong_double_ and
associated macros for other types, leaving only the macro _Mdouble_
which is actually used as the type for which a given inclusion of
<bits/mathcalls.h> should declared functions.

Tested for x86_64, and tested with build-many-glibcs.py that installed
stripped shared libraries are unchanged by this patch.

	* math/math.h [!_Mfloat_] (_Mfloat_): Do not define.
	[!_Mlong_double_] (_Mlong_double_): Likewise.
	[!_Mfloat16_] (_Mfloat16_): Likewise.
	[!_Mfloat32_] (_Mfloat32_): Likewise.
	[!_Mfloat64_] (_Mfloat64_): Likewise.
	[!_Mfloat128_] (_Mfloat128_): Likewise.
	[!_Mfloat32x_] (_Mfloat32x_): Likewise.
	[!_Mfloat64x_] (_Mfloat64x_): Likewise.
	[!_Mfloat128x_] (_Mfloat128x_): Likewise.
	(_Mdouble_): Define without indirection through those macros.
	* math/complex.h [!_Mfloat_] (_Mfloat_): Do not define.
	[!_Mfloat128_] (_Mfloat128_): Likewise.
	[_Mlong_double_] (_Mlong_double_): Likewise.
	(_Mdouble_): Define without indirection through those macros.
	* math/Makefile [$(long-double-fcts) != yes] (math-CPPFLAGS): Do
	not add -D_Mlong_double_=double.
	* include/math.h [_ISOMAC] (_Mlong_double_): Do not undefine.
	* math/test-signgam-finite-c99.c (_Mlong_double_): Likewise.