common.mk: integrate clean targets

* common.mk (clean-rdoc, clean-capi, clean-platform): integrate
  from Makefile.in and win32/Makefile.sub.

* win32/Makefile.sub (RMALL): now use rm.bat instead of rmall.bat
  which does not handle any options and convert slashes.

* win32/rmall.bat: no longer used.  use rm.bat with -r instead.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46750 b2dd03c8-39d4-4d8f-98ff-823fe69b080e