libstdc++: Add copyright and license text to new generated headers

contrib/ChangeLog:

	* unicode/gen_libstdcxx_unicode_data.py: Add copyright and
	license text to the output.

libstdc++-v3/ChangeLog:

	* include/bits/text_encoding-data.h: Regenerate.
	* include/bits/unicode-data.h: Regenerate.
	* scripts/gen_text_encoding_data.py: Add copyright and license
	text to the output.