* Changes in the autotools stuff affecting a lot of platform dependent

* Changes in the autotools stuff affecting a lot of platform dependent
  code. Now we have a platform (maemo/gnome) and a toolkit (gtk, hildon1
  and hildon2).
* hildon2 is still pointing to maemo directory. But this change will
  enable us to begin the hildon2 port work in a different folder.
* The change is also important for MID compatibility, as it's platform
  would be gnome, and the toolkit a hildon flavor.
* Removed the HAVE_HILDON0_WIDGETS and similars. Now we have a
  MODEST_HILDON_API variable with the major number of the hildon
  library.

pmo-trunk-r5822