Added some info that came up on fltk.general:
Subject: README mods [was: Fl_Choice crash on 1.3.2 on MacOS]
    o Special instructions for svn checkout to use 'make makeinclude'
    o Added list of commonly used make targets



git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10107 ea41ed52-d2ee-0310-a9c1-e6b18d33e121