separate files under directories due to directory separator.
* */Makefile.sub (MKFILES): common.mk and */Makefile.sub should not be
removed.
* win32/Makefile.sub, wince/Makefile.sub: $* cannot appear in explicit
rules.
* cygwin/GNUmakefile.in: some mingw stuffs were missed.
* lib/mkmf.rb (create_makefile): Borland make wrongly removes braces
from command lines.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@6001 b2dd03c8-39d4-4d8f-98ff-823fe69b080e