Separate out the UI from the program logic

The following are UI toolkit specific:
gtk-gui.c   - overall layout, main window of the UI
divelist.c  - list of dives subsurface maintains
equipment.c - equipment / tank information for each dive
info.c      - detailed dive info
print.c     - printing

The rest is independent of the UI:
main.c i    - program frame
dive.c i    - creates and maintaines the internal dive list structure
libdivecomputer.c
uemis.c
parse-xml.c
save-xml.c  - interface with dive computers and the XML files
profile.c   - creates the data for the profile and draws it using cairo

This commit should contain NO functional changes, just moving code around
and a couple of minor abstractions.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

display.h

@@ -1,23 +1,8 @@
 #ifndef DISPLAY_H
 #define DISPLAY_H
 
-#include <gtk/gtk.h>
-#include <gdk/gdk.h>
 #include <cairo.h>
 
-extern GtkWidget *main_window;
-
-extern const char *divelist_font;
-extern void set_divelist_font(const char *);
-
-extern void import_dialog(GtkWidget *, gpointer);
-extern void report_error(GError* error);
-
-extern GtkWidget *dive_profile_widget(void);
-extern GtkWidget *dive_info_frame(void);
-extern GtkWidget *extended_dive_info_widget(void);
-extern GtkWidget *equipment_widget(void);
-
 extern void repaint_dive(void);
 extern void do_print(void);
 
@@ -38,5 +23,6 @@ struct graphics_context {
 };
 
 extern void plot(struct graphics_context *gc, int w, int h, struct dive *dive);
+extern void set_source_rgb(struct graphics_context *gc, double r, double g, double b);
 
 #endif