Make the LoopRotate pass's maximum header size configurable both programmatically
and via the command line, mirroring similar functionality in LoopUnroll.  In
situations where clients used custom unrolling thresholds, their intent could
previously be foiled by LoopRotate having a hardcoded threshold.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209617 91177308-0d34-0410-b5e6-96231b3b80d8