Add runtime hook to create PyQt5.Qt 'Composite Module'

PyQt5 exposes the PyQt5.Qt module which contains symbols from all other PyQt5
packages. PyQt5 uses Python's C API to import all modules and merge their
contents with PyQt5.Qt (see the generated sipQtcmodule.c file when compiling
PyQt5), but due to a bug in PyQt, it seems to skip all import-hooks machinery.

Here, we replicate what PyQt does but using native Python code, which we know
won't bypass the import hooks mechanism described in PEP-302.
Merge pull request #128 from lvillani/pyqt5-composite-module

Add runtime hook to create PyQt5.Qt 'Composite Module'.
Add hook for Python Xlib wrapper
Normalize TOC "DATA" paths to prevent multiple inclusion on Windows

This is implements the patch suggested on
http://www.pyinstaller.org/ticket/783

This should also fix a similar problem on OS X when
case-insensitive HFS+ is used.
Make it possible to encrypt Python bytecode