Revert revert of r362112 with minor SystemZ test file corrections.

[FPEnv] Added a special UnrollVectorOp method to deal with the chain on StrictFP opcodes

This change creates UnrollVectorOp_StrictFP. The purpose of this is to address a failure that consistently occurs when calling StrictFP functions on vectors whose number of elements is 3 + 2n on most platforms, such as PowerPC or SystemZ. The old UnrollVectorOp method does not expect that the vector that it will unroll will have a chain, so it has an assert that prevents it from running if this is the case. This new StrictFP version of the method deals with the chain while unrolling the vector. With this new function in place during vector widending, llc can run vector-constrained-fp-intrinsics.ll for SystemZ successfully.

Submitted by:	Drew Wock <drew.wock@sas.com>
Reviewed by:	Cameron McInally, Kevin P. Neal
Approved by:	Cameron McInally
Differential Revision:	https://reviews.llvm.org/D62546

llvm-svn: 362241