contrib: add copyright for my scripts

contrib/ChangeLog:

	* analyze_brprob.py: Add copyright header.
	* analyze_brprob_spec.py: Likewise.
	* check-params-in-docs.py: Likewise.
	* check_GNU_style.py: Likewise.
	* check_GNU_style_lib.py: Likewise.
	* filter-clang-warnings.py: Likewise.
	* gcc-changelog/git_check_commit.py: Likewise.
	* gcc-changelog/git_commit.py: Likewise.
	* gcc-changelog/git_email.py: Likewise.
	* gcc-changelog/git_repository.py: Likewise.
	* gcc-changelog/git_update_version.py: Likewise.
	* gcc-changelog/test_email.py: Likewise.
	* mark_spam.py: Likewise.