[PATCH] Removed pattern checks in instruction simplify/ combine which are now handled in SimplifyUsingDistributiveLaws()

[Dinesh Dwivedi]

Yes, With SimplifyUsingDistributiveLaws() updated in r211261, now it can handle all transforms
handled by these removed code. This patch removes code duplication. I am planning to further
analyse transform using associative, commutative and distributive laws and generalize them.

I had doubt about removing code from instruction simplify as it works as independent pass. I have
talked to Ben before submitting this patch for review.

I do have my doubts about what goes to simplify and what in combine. But from what I have read
in code and mailing list, if we can transform instruction to one of its operand or to some simple 
value, it should be in simplify. Instruction combine has transforms which combine 2 or more 
instruction to less instruction(s).

http://reviews.llvm.org/D4253