[PATCH] [X86][SSE] Vector integer/float conversion memory folding

[Simon Pilgrim]

I'll split the cvttp*todq fix from the cvtdq2ps patch and add extra tests to the avx1-stack-reload-folding.ll 

BTW I could have added AVX-512 equivalents as well but have no hardware to test it on....

Does the third part of the patch need review? Its pretty benign.

http://reviews.llvm.org/D5981