[X86] Make __builtin_ia32_vec_ext_v2si require ICE for its index argument. Add...

[X86] Make __builtin_ia32_vec_ext_v2si require ICE for its index argument. Add warnings for out of range indices for __builtin_ia32_vec_ext_v2si, __builtin_ia32_vec_ext_v4hi, and __builtin_ia32_vec_set_v4hi.

These should take a constant value for an index and that constant should be a valid element number.

llvm-svn: 334051