fix Issue 13289 - wchar and dchar C++ mangling is incorrect

Conflicts:
	test/runnable/cppa.d
	test/runnable/extra-files/cppb.cpp
Merge pull request #3869 from dragoon2014/master

Fix wchar and dchar C++ mangling
fix Issue 13394 - invariant fail to link since 2.066 when using separate compilation