Set sourcepkg to pkgname through run_template().

This removes the need for having to specify sourcepkg manually in
every package that will build subpkgs.

--HG--
extra : convert_revision : 383e4c467e84844d2f4f61ae5c5e07a5124e9cfb

templates/startup-notification/template

@@ -1,6 +1,5 @@
 # Template build file for 'startup-notification'.
 pkgname=startup-notification
-sourcepkg=$pkgname
 version=0.10
 distfiles="http://www.freedesktop.org/software/$pkgname/releases/$pkgname-$version.tar.gz"
 build_style=gnu_configure