Fix #if tests for PTRACE_GETREGS and others.

Summary:
On PowerPC64 Linux PTRACE_GETREGS is a #define and PT_GETREGS is not.
On other systems it's the other way round. Extend the #ifs to check for
both PTRACE_* and PT_*.

This fixes test/sanitizer_common/TestCases/Linux/ptrace.cc when msan is
enabled for PowerPC64.

Reviewers: zatrazz, kcc, eugenis, samsonov

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14564

llvm-svn: 252730