Add support for load folding of avx1 logical instructions

AVX supports logical operations using an operand from memory. Unfortunately
because integer operations were not added until AVX2 the AVX1 logical
operation's types were preventing the isel from folding the loads. In a limited
number of cases the peephole optimizer would fold the loads, but most were
missed. This patch adds explicit patterns with appropriate casts in order for
these loads to be folded.

The included test cases run on reduced examples and disable the peephole
optimizer to ensure the folds are being pattern matched.

Patch by Louis Gerbarg <lgg@apple.com>

rdar://16355124