Bindings: Add support for scoped enums

Summary:
Keep the enum intact by emitting the class keyword in case the enum is
scoped.
Use the complete enum scope for parameter values, the enclosing scope is
only correct to use for unscoped enums.
The python Cursor.is_scoped_enum() method has been added with LLVM/Clang
version 5.0.

BUG: 397154

Test Plan: build kcoreaddons

Reviewers: #frameworks, mpyne

Reviewed By: mpyne

Subscribers: mpyne, kde-frameworks-devel, kde-buildsystem

Tags: #frameworks, #build_system

Differential Revision: https://phabricator.kde.org/D14908