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/tcp_wrappers/template

@@ -1,6 +1,5 @@
 # Template file for 'tcp_wrappers'
 pkgname=tcp_wrappers
-sourcepkg=$pkgname
 version=7.6
 wrksrc="${pkgname}_${version}"
 patch_files="shared_lib_plus_plus-1.diff"