The compilation of the WRaster library needs the keyword
EXTRA_*_DEPENDENCIES in its Makefile so the configure.ac have been updated
to require at least the version of automake in which it is added.
Reported-by: Josip Deanovic <djosip+news@linuxpages.net>
Signed-off-by: Christophe CURIS <christophe.curis@free.fr>