Use LineLocation instead of CallsiteLocation to index callsite profile.

Use LineLocation instead of CallsiteLocation to index callsite profile.

Summary: With discriminator, LineLocation can uniquely identify a callsite without the need to specifying callee name. Remove Callee function name from the key, and put it in the value (FunctionSamples).

Reviewers: davidxl, dnovillo

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D17827

llvm-svn: 262634