[XRay][compiler-rt] Remove C++ STL from the buffer queue implementation

Summary:
This change removes the dependency on C++ standard library
types/functions in the implementation of the buffer queue. This is an
incremental step in resolving llvm.org/PR32274.

Reviewers: dblaikie, pelikan

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D39175

llvm-svn: 316406