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/xf86-input-synaptics/template

@@ -1,6 +1,5 @@
 # Template build file for 'xf86-input-synaptics'.
 pkgname=xf86-input-synaptics
-sourcepkg=$pkgname
 version=1.1.0
 distfiles="${XORG_SITE}/driver/$pkgname-$version.tar.bz2"
 build_style=gnu_configure