Add filters for D language sources to contrib/update-copyright.py

2018-11-26  Iain Buclaw  <ibuclaw@gdcproject.org>

	* update-copyright.py (TestsuiteFilter): Skip .d tests.
	(LibPhobosFilter): Add filter for upstream D sources.
	(GCCCopyright): Add D Language Foundation as external author.
	(GCCCmdLine): Add libphobos.

From-SVN: r266491