add -std=gnu89 to allow compile with clang and -O0


git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/gdl2/trunk@36292 72102866-910b-0410-8b05-ffd578937521
        * EOControl/EOPrivate.h
          do not access the isa directly, use object_getClass



git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/gdl2/trunk@36293 72102866-910b-0410-8b05-ffd578937521