Valama Autotools: Drop prepared flag.
Valama Autotools: Fix build path.

 * Bug introduced by f3fcc1e.
Valama Autotools: Remove creation date from configure.ac.

 * Synchronize this with CMake build system. As long as there is no check for
   same content a time doesn't make sense (only shows when you compile the
   project).
Valama Autotools: Don't add packages without pc file.
Valama: Fix first build system selection.

 * Set default build system in welcome_screen (according to template).
Valama: Add global threads option for make commands.

 * Add configurable (no config implemented yet) option to control make options
   in one place.
Valama: Check for Makefile existance for clean command.

 * For make clean command obviously the Makefile needs to exist.
 * Update CMake distclean check.
Valama Autotools: Fix distclean.

 * Copy clean, just with distclean target this time.