rs6000-builtin.def: Change VSIGNED2 and VUNSIGNED2 macro expansions from BU_VSX_2 to BU_P8V_VSX_2...

gcc/ChangeLog:

2018-02-23  Carl Love  <cel@us.ibm.com>

	* config/rs6000/rs6000-builtin.def: Change VSIGNED2 and VUNSIGNED2
	macro expansions from BU_VSX_2 to BU_P8V_VSX_2 and BU_VSX_OVERLOAD_2 to
	BU_P8V_OVERLOAD_2.
	* config/rs6000/rs6000-c.c: Change VSX_BUILTIN_VEC_VSIGNED2 to
	P8V_BUILTIN_VEC_VSIGNED2.  Change VSX_BUILTIN_VEC_VUNSIGNED2 to
	P8V_BUILTIN_VEC_VUNSIGNED2.

gcc/testsuite/ChangeLog:

2018-02-23  Carl Love  <cel@us.ibm.com>

	* gcc.target/powerpc/builtins-3-runnable.c: Move tests for vec_float2,
	vec_signed2 and vec_unsigned2 to new Power 8 test file.
	* gcc.target/powerpc/builtins-3-runnable-p8.c: New test file for
	Power 8 tests.

From-SVN: r257937