added sys_getch

git-svn-id: http://ocamllibs.googlecode.com/svn/trunk@281 21970f9d-2756-cbab-44b1-85fcaa48d7c2
fix

git-svn-id: http://ocamllibs.googlecode.com/svn/trunk@282 21970f9d-2756-cbab-44b1-85fcaa48d7c2
added missing header

git-svn-id: http://ocamllibs.googlecode.com/svn/trunk@283 21970f9d-2756-cbab-44b1-85fcaa48d7c2