Disables gimple folding for VSX_BUILTIN_XVMINDP, VSX_BUILTIN_XVMAXDP,ALTIVEC_BUILTIN_...

Disables gimple folding for VSX_BUILTIN_XVMINDP, VSX_BUILTIN_XVMAXDP,ALTIVEC_BUILTIN_VMINFP and ALTIVEC_BUILTIN_VMAXFP when fast-math is not set.

gcc/
	* config/rs6000/rs6000-call.c (rs6000_gimple_fold_builtin): Disable
	gimple fold for VSX_BUILTIN_XVMINDP, ALTIVEC_BUILTIN_VMINFP,
	VSX_BUILTIN_XVMAXDP, ALTIVEC_BUILTIN_VMAXFP when fast-math is not
	set.

gcc/testsuite/
	* gcc.target/powerpc/vec-minmax-1.c: New test.
	* gcc.target/powerpc/vec-minmax-2.c: Likewise.