Modify Cflags in package-config files

Cflags in pkg-config files sets the include path
to $PREFIX/openflow, $PREFIX/openvswitch. This makes
the including source files use the files like
  include <util.h>
instead of
  include <openvswitch/util.h>

Also fixed a missing "\" in make-file.

Signed-off-by: Amit Bose <bose@noironetworks.com>