Fast-math flags for LLVM IR parsing and printing

Fast-math flags for LLVM IR parsing and printing

Added in the ability to read LLVM IR text that contains fast-math flags as a sequence of capital letters separated by spaces in any order. Added in the printing of the fast-math flags in a canonical order, and don't print the other flags when 'fast' is specified, as 'fast' implies all the others.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168645 91177308-0d34-0410-b5e6-96231b3b80d8