Issue #507: Implement method load_module by FrozenImporter class as required by PEP302.
Issue #507: Add BuiltinImporter class and fixes for load_module() in FrozenImporter.
Issue #507: Implement PEP302 compatible importer for C extension modules.
Issue #507: Better exception handling in new importer classes.
Issue #507: Remove old importers that directly overrided built-in import machinery.
Issue #507: Fix test basic/test_module_attributes for new import machinery.
Issue #507: Fix test import/test_relative_import3 for new import machinery.
Issue #507: Fix PIL.Image runtime hooks for new import machinery.
Issue #507: Fix for the wx tests - do not keep __path__ attribute empty list.
Issue #507: Fix for the celementtree tests - do not add sys.prefix to  __path__ attribute.
Issue #507: Fix for the pyttsx test on Windows - do not set attribute __loader__ for frozen imports.
Issue #507: Cleanup of pyi_iu.py.
Issue #507: Fix code depending on old pyi_iu.py.
Issue #507: Fix test basic/test_module_attributes.
Clean: Print processed hooks to console while creating frozen executable.
Issue #424: Add option --runtime-hook for bundling custom runtime hook files.
Merge remote-tracking branch 'upstream/develop' into develop
Issue #654: Implement method loader.is_package() for FrozenImporter.
Issue #654: Implement method loader.get_code() and get_source() for PEP302 import hooks.
Issue #654: Add test for some pep302 extension methods.