Use bash features to improve $distfiles parsing.

That means that it's not necessary anymore to use an '@' before the
extract suffix string. yay.

--HG--
extra : convert_revision : 83ce2c783cb917ef59b87eacb0565cfcff277218

templates/gtk-sharp.tmpl

@@ -2,7 +2,7 @@
 pkgname=gtk-sharp
 version=2.12.4
 distfiles="
-http://ftp.gnome.org/pub/gnome/sources/gtk-sharp/2.12/$pkgname-$version@.tar.bz2"
+http://ftp.gnome.org/pub/gnome/sources/gtk-sharp/2.12/$pkgname-$version.tar.bz2"
 build_style=gnu_configure
 make_cmd="$XBPS_MASTERDIR/bin/gmake"
 pkgconfig_override="gtk-sharp-2.0.pc gtk-dotnet-2.0.pc glib-sharp-2.0.pc