input files for code generators into defs/ directory.
* Makefile.in (lex.c): followed keywords and lex.c.src.
* common.mk (parser.o): followed keywords.
(INSNS): followed opt_*.def
* tools/instruction.rb: followed opt_*.def.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@19844 b2dd03c8-39d4-4d8f-98ff-823fe69b080e