[SystemZ] Add support for IBM z14 processor (3/3)

This patch updates the vecintrin.h header file to provide the new
set of high-level vector built-in functions.  This matches the
updated definition implemented by other compilers for the platform,
indicated by the pre-defined macro __VEC__ == 10302.

Note that some of the new functions (notably those involving the
vector float data type) are only available with -march=z14
(indicated by __ARCH__ == 12).

llvm-svn: 308199