giscanner: Add New CCompiler Module

This adds a CCompiler module for the giscanner Python scripts so that items
related to the run of the preprocessor, compiler and linker can be done in
this module, and this marks the beginning of the move of building the
introspection files using Python's distutils.

This patch first moves _add_[internal|external]_link_flags() to
ccompiler.py as get_[internal|external]_link_flags and also moves the
Windows shlibs resolution (deducing the DLLs the introspection files should
link to from the libraries passed in) in shlibs.py to
resolve_windows_libs() in ccompiler.py

https://bugzilla.gnome.org/show_bug.cgi?id=728313