Major changes to support multiple distfiles in templates.

Each template now needs to use $distfiles that accepts the full
URL to download the distfile and old $extract_sufx is now merged
on it, but this must be separated by the '@' character. Example:

distfiles="http://www.foo.org/blah-6.2@.tar.gz
http://www.foo.org/blob-1.0@.tar.bz2"

If distfiles contains multiple files defined, $wrksrc is now
mandatory.

--HG--
extra : convert_revision : 1c3fa35f148af8323ce3cbcf5732104960de6bc4

templates/xorg-server.tmpl

@@ -2,8 +2,8 @@
 pkgname=xorg-server
 version=1.5.1
 patch_files="$pkgname-dix-getevents-c.diff"
-extract_sufx=".tar.bz2"
-url=http://xorg.freedesktop.org/releases/individual/xserver
+distfiles="
+http://xorg.freedesktop.org/releases/individual/xserver/$pkgname-$version@.tar.bz2"
 build_style=gnu_configure
 configure_args="--with-xkb-path=$XBPS_MASTERDIR/share/X11/xkb
  --with-xkb-output=$XBPS_MASTERDIR/var/db/xkb --enable-install-setuid