Add new intrinsics for Neon VTRN, VZIP and VUZP operations. Modeling these

as vector shuffles did not work out well.  Shuffles that produce double-wide
vectors accurately represent the operation but make it hard to do anything
with the results.  I considered splitting them up into 2 shuffles, one to
write each register separately, but there doesn't seem to be a good way to
reunite them for codegen.

llvm-svn: 78437