win32/setup.mak: separate verconf.mk

* win32/setup.mak (verconf.mk): separate RUBY_RELEASE_DATE from
  Makefile so that build would not stop everyday.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46393 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
win32/setup.mak: rename RUBY_RELEASE_DATE

* win32/setup.mak (verconf.mk): rename RUBY_PROGRAM_VERSION as
  RUBY_RELEASE_DATE, same as other platforms.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46394 b2dd03c8-39d4-4d8f-98ff-823fe69b080e