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/glproto.tmpl

@@ -2,7 +2,7 @@
 pkgname=glproto
 version=1.4.9
 distfiles="
-http://xorg.freedesktop.org/releases/individual/proto/$pkgname-$version@.tar.bz2"
+http://xorg.freedesktop.org/releases/individual/proto/$pkgname-$version.tar.bz2"
 build_style=gnu_configure
 pkgconfig_override="glproto.pc"
 short_desc="GL extension headers"