Implementation of Intel(R) Processor Trace support for Linux

Summary:
This patch implements support for Intel(R) Processor Trace
in lldb server. The changes have support for
starting/stopping and reading the trace data. The code
is only available on Linux versions where the perf
attributes for aux buffers are available.

The patch also consists of Unit tests for testing the
core buffer reading function.

Reviewers: lldb-commits, labath, clayborg, zturner, tberghammer

Reviewed By: labath, clayborg

Subscribers: mgorny

Differential Revision: https://reviews.llvm.org/D33674

llvm-svn: 306516