update Unicode version (and Emoji version) to 12.0.0

	- common.mk: set UNICODE_VERSION and UNICODE_EMOJI_VERSION to 12.0.0

	- lib/unicode_normalize/tables.rb: update table data to Unicode version 12.0.0

	- enc/unicode/12.0.0/casefold.h, enc/unicode/12.0.0/name2ctype.h: add generated
	  files for Unicode version 12.0.0

	This is the main commit for #15321.

	add news about Unicode version update (issue #15321) to NEWS [ci skip]

	delete directory and files related to Unicode version 11.0.0

	this completes and closes feature #15321

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_6@67175 b2dd03c8-39d4-4d8f-98ff-823fe69b080e