gallivm: don't use integer min/max sse intrinsics with llvm >= 3.9

gallivm: don't use integer min/max sse intrinsics with llvm >= 3.9

Apparently, these are deprecated. There's some AutoUpgrade feature which
is supposed to promote these to cmp/select, which apparently doesn't work
with jit code. It is possible it's not actually even meant to work (see
the bug filed against llvm which couldn't provide an answer neither)
but in any case this is meant to be only temporary unless the intrinsics
are really illegal. So, just use the fallback code (which should be cmp/select,
we're actually doing cmp/sext/trunc/select, but in any case llvm 3.9 manages
to optimize this back to pmin/pmax in the end).

This addresses https://llvm.org/bugs/show_bug.cgi?id=28176

CC: <mesa-stable@lists.freedesktop.org>
Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
Tested-by: Vinson Lee <vlee@freedesktop.org>
Tested-by: Aaron Watry <awatry@gmail.com>