Move ROUNDING_TESTS_* out of math-tests.h.

Move ROUNDING_TESTS_* out of math-tests.h.

Continuing moving macros out of math-tests.h to smaller headers
following typo-proof conventions instead of using #ifndef, this patch
moves the ROUNDING_TESTS_* macros for individual types out to their
own sysdeps header.

In the soft-float case where FE_TONEAREST is the only rounding mode
macro defined, there is no need to define ROUNDING_TESTS_*; it is only
necessary when rounding modes macros are defined that may not be
supported at runtime.  Thus, the ROUNDING_TESTS_* definitions for some
configurations are just removed, not moved to new
math-tests-rounding.h headers; the only architectures needing
math-tests-rounding.h are those where the macros are defined in
bits/fenv.h because of the possibility of a soft-float compilation
using a hard-float glibc with the same ABI (i.e., ARM and RISC-V).

The test-*-vlen*.h headers, by using #undef, do not yet follow
typo-proof conventions (but they no longer implicitly rely on being
included before math-tests.h, and this area can always be cleaned up
further in future).

Tested with build-many-glibcs.py.

	* sysdeps/generic/math-tests-rounding.h: New file.
	* sysdeps/generic/math-tests.h: Include <math-tests-rounding.h>.
	(ROUNDING_TESTS_float): Do not define here.
	(ROUNDING_TESTS_double): Likewise.
	(ROUNDING_TESTS_long_double): Likewise.
	(ROUNDING_TESTS_float128): Likewise.
	* math/test-double-vlen2.h: Include <math-tests-rounding.h>.
	(ROUNDING_TESTS_double): Undefine before defining.
	* math/test-double-vlen4.h: Include <math-tests-rounding.h>.
	(ROUNDING_TESTS_double): Undefine before defining.
	* math/test-double-vlen8.h: Include <math-tests-rounding.h>.
	(ROUNDING_TESTS_double): Undefine before defining.
	* math/test-float-vlen16.h: Include <math-tests-rounding.h>.
	(ROUNDING_TESTS_float): Undefine before defining.
	* math/test-float-vlen4.h: Include <math-tests-rounding.h>.
	(ROUNDING_TESTS_float): Undefine before defining.
	* math/test-float-vlen8.h: Include <math-tests-rounding.h>.
	(ROUNDING_TESTS_float): Undefine before defining.
	* sysdeps/arm/nofpu/math-tests-rounding.h: New file.
	* sysdeps/arm/math-tests.h [__SOFTFP__] (ROUNDING_TESTS_float): Do
	not define here.
	[__SOFTFP__] (ROUNDING_TESTS_double): Likewise.
	[__SOFTFP__] (ROUNDING_TESTS_long_double): Likewise.
	* sysdeps/riscv/nofpu/math-tests-rounding.h: New file.
	* sysdeps/riscv/math-tests.h [!__riscv_flen]
	(ROUNDING_TESTS_float): Do not define here.
	[!__riscv_flen] (ROUNDING_TESTS_double): Likewise.
	[!__risv_flen] (ROUNDING_TESTS_long_double): Likewise.
	* sysdeps/m68k/coldfire/math-tests.h [!__mcffpu__]
	(ROUNDING_TESTS_float): Likewise.
	[!__mcffpu__] (ROUNDING_TESTS_double): Likewise.
	[!__mcffpu__] (ROUNDING_TESTS_long_double): Likewise.
	* sysdeps/mips/math-tests.h [__mips_soft_float]
	(ROUNDING_TESTS_float): Likewise.
	[__mips_soft_float] (ROUNDING_TESTS_double): Likewise.
	[__mips_soft_float] (ROUNDING_TESTS_long_double): Likewise.
	* sysdeps/nios2/math-tests.h (ROUNDING_TESTS_float): Likewise.
	(ROUNDING_TESTS_double): Likewise.
	(ROUNDING_TESTS_long_double): Likewise.