e: stop warning about GNU make extension

We know wildcard is an extension of GNU make and we don't need to be
remembered every single compilation. Remove noise like below:

doc/Makefile.am:42: warning: wildcard img/*.*: non-POSIX variable name
doc/Makefile.am:42: (probably a GNU make extension)



SVN revision: 78723

autogen.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-autoreconf --symlink --install
+autoreconf --symlink --install -Wno-portability
 
 if [ -z "$NOCONFIGURE" ]; then
 	./configure -C "$@"