Build SymbolMap in SampleProfileLoader to help matchin function names with suffix.

Summary: If there is suffix added in the function name (e.g. module hash added by thinLTO), we will not be able to find a match in profile as the suffix does not exist in profile. This patch build a map from function name to Function *. The map includes the entry for the stripped function name so that inlineHotFunctions can find the corresponding function to promote/inline.

Reviewers: davidxl, dnovillo, tejohnson

Reviewed By: davidxl

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D31952

llvm-svn: 300507