libstdc++: Use a PCH to speed up check-simd

libstdc++: Use a PCH to speed up check-simd

Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
libstdc++-v3/ChangeLog:

	* testsuite/experimental/simd/generate_makefile.sh: Generate and
	pre-compile pch.h, which includes all headers that do not depend
	on command-line macros.
	* testsuite/experimental/simd/tests/bits/main.h: New file.
	(iterate_abis, main): Moved from verify.h.
	* testsuite/experimental/simd/tests/bits/verify.h
	(iterate_abis, main): Moved to main.h.
	* testsuite/experimental/simd/tests/bits/conversions.h: Add
	include guard.
	(genHalfBits): Simplify.
	* testsuite/experimental/simd/tests/bits/make_vec.h: Add include
	guard.
	(make_alternating_mask): Moved from mask_loadstore.
	* testsuite/experimental/simd/tests/bits/mathreference.h: Add
	include guard.
	* testsuite/experimental/simd/tests/bits/test_values.h: Ditto.
	* testsuite/experimental/simd/tests/mask_loadstore.cc
	(make_mask, make_alternating_mask): Removed.
	* testsuite/experimental/simd/tests/mask_reductions.cc: Ditto.
	* testsuite/experimental/simd/tests/operators.cc (genHalfBits):
	Removed.
	* testsuite/experimental/simd/tests/abs.cc: Only include
	bits/main.h.
	Ditto.
	* testsuite/experimental/simd/tests/algorithms.cc: Ditto.
	* testsuite/experimental/simd/tests/broadcast.cc: Ditto.
	* testsuite/experimental/simd/tests/casts.cc: Ditto.
	* testsuite/experimental/simd/tests/fpclassify.cc: Ditto.
	* testsuite/experimental/simd/tests/frexp.cc: Ditto.
	* testsuite/experimental/simd/tests/generator.cc: Ditto.
	* testsuite/experimental/simd/tests/hypot3_fma.cc: Ditto.
	* testsuite/experimental/simd/tests/integer_operators.cc: Ditto.
	* testsuite/experimental/simd/tests/ldexp_scalbn_scalbln_modf.cc:
	* testsuite/experimental/simd/tests/loadstore.cc: Ditto.
	* testsuite/experimental/simd/tests/logarithm.cc: Ditto.
	* testsuite/experimental/simd/tests/mask_broadcast.cc: Ditto.
	* testsuite/experimental/simd/tests/mask_conversions.cc: Ditto.
	* testsuite/experimental/simd/tests/mask_implicit_cvt.cc: Ditto.
	* testsuite/experimental/simd/tests/mask_operator_cvt.cc: Ditto.
	* testsuite/experimental/simd/tests/mask_operators.cc: Ditto.
	* testsuite/experimental/simd/tests/math_1arg.cc: Ditto.
	* testsuite/experimental/simd/tests/math_2arg.cc: Ditto.
	* testsuite/experimental/simd/tests/operator_cvt.cc: Ditto.
	* testsuite/experimental/simd/tests/reductions.cc: Ditto.
	* testsuite/experimental/simd/tests/remqo.cc: Ditto.
	* testsuite/experimental/simd/tests/simd.cc: Ditto.
	* testsuite/experimental/simd/tests/sincos.cc: Ditto.
	* testsuite/experimental/simd/tests/split_concat.cc: Ditto.
	* testsuite/experimental/simd/tests/splits.cc: Ditto.
	* testsuite/experimental/simd/tests/trigonometric.cc: Ditto.
	* testsuite/experimental/simd/tests/trunc_ceil_floor.cc: Ditto.
	* testsuite/experimental/simd/tests/where.cc: Ditto.