[x86] Remove the 2-addr-to-3-addr "optimization" from shufps to pshufd.

This trades a (register-renamer-friendly) movaps for a floating point
/ integer domain cross. That is a very bad trade, even on architectures
where domain crossing is relatively fast. On any chip where there is
even a cycle stall, this is a Very Bad Idea. It doesn't even seem likely
to cause a spill to be introduced because the reason for the copy is to
destructively shuffle in place.

Thanks to Ben Kramer for fixing a bug in this code that my new shuffle
lowering exposed and highlighting that perhaps it should just go away.
=]
[clang-tidy] Allow space between "TODO" and "(user)"
Give the Reassociate pass a bit more flexibility and autonomy when optimizing expressions.
Particularly, it addresses cases where Reassociate breaks Subtracts but then fails to optimize combinations like I1 + -I2 where I1 and I2 have the same rank and are identical.

Patch by Dmitri Shtilman.
PE/COFF: add a check to ensure that we dont mix up architectures

Previously, we would not check the target machine type and the module (object)
machine type.  Add a check to ensure that we do not attempt to use an object
file with a different target architecture.

This change identified a couple of tests which were incorrectly mixing up
architecture types, using x86 input for a x64 target.  Adjust the tests
appropriately.  The renaming of the input and the architectures covers the
changes to the existing tests.

One significant change to the existing tests is that the newly added test input
for x64 uses the correct user label prefix for X64.