common.mk: verconf.h for parallel build

* common.mk (verconf.h): depend on the timestamp file instead of
  rbconfig.rb, for parallel build.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40777 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
generic_erb.rb: --source option

* tool/generic_erb.rb: -x, --source option for debug.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40778 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
verconf.h.in: template for verconf.h

* template/verconf.h.in: generate verconf.h from the template and
  rbconfig.rb.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40779 b2dd03c8-39d4-4d8f-98ff-823fe69b080e