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/mono.tmpl

@@ -1,7 +1,7 @@
 # Template build file for 'mono'.
 pkgname=mono
 version=2.0
-distfiles="http://ftp.novell.com/pub/mono/sources/mono/$pkgname-$version@.tar.bz2"
+distfiles="http://ftp.novell.com/pub/mono/sources/mono/$pkgname-$version.tar.bz2"
 tar_override_cmd="$XBPS_MASTERDIR/bin/gtar"
 build_style=gnu_configure
 configure_args="--with-icu=yes --with-preview=yes --with-libgdiplus=installed