Remove option from old VimOrganizer plugin

I do not use this plugin any more.
Cygwin replaced mlcscope with cscope

Support both. I'm not sure what the difference is, but I want to make
sure it always works.

According to [1] cscope obsoletes mlcscope (which "was from 2006"), so
prefer cscope if available.

[1] http://comments.gmane.org/gmane.os.cygwin.applications/24453