xbps-src: multiple improvements to messages and phases.

- Prefix all messages with 'Package 'pkgname (version)': ..." to really
  understand what's going on. Add more messages in some stages...
- Do not run pre/post_{configure,build,install} or do_{build,install} stages
  if they were executed successfully in the past.

xbps-src/shutils/common_funcs.sh

@@ -36,6 +36,7 @@ run_func()
 		$func
 		return $?
 	fi
+	return 255 # function not found.
 }
 
 msg_red()