Add gdb pretty printers for a wide variety of libc++ data structures.

Summary: Also add a test suite.

Reviewers: EricWF

Subscribers: christof, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65609

Run a pep8 formatter.

Run pep8 formatter.

Convert to PEP8, address other comments from code review.

llvm-svn: 370551