[XRay][compiler-rt][NFC] Turn ProudCase functions to humbleCase functions

Summary:
As pointed out in casual reading of the XRay codebase, that we had
some interesting named functions that didn't quite follow the LLVM coding
conventions.

Reviewers: chandlerc, dblaikie

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29625

llvm-svn: 294373