Load tiles in true spiral pattern
Load tiles in true spiral pattern

Despite author's comment, the tiles were _not_ loaded in concentric squares
(hint: the number of tiles present one square is not equal to 4*side_size).
This patch loads tiles in true spiral manner, which, apart from not loading
the same tile several times, also looks much nicer.

Signed-off-by: Jiří Techet <af18a4329e30c3b95edc4d3e647176d16d87c9c7@gmail.com>

PabloCastellano/libchamplain,GNOME/perl-Champlain,potyl/champlain,StanciuMarius/Libchamplain-map-wrapping,GNOME/perl-Gtk2-Champlain,Distrotech/libchamplain,StanciuMarius/Libchamplain-map-wrapping,GNOME/libchamplain,Distrotech/libchamplain,PabloCastellano/libchamplain,StanciuMarius/Libchamplain-map-wrapping,PabloCastellano/libchamplain,GNOME/perl-Champlain,GNOME/perl-Gtk2-Champlain,potyl/champlain,StanciuMarius/Libchamplain-map-wrapping,Distrotech/libchamplain,Distrotech/libchamplain,potyl/champlain,PabloCastellano/libchamplain,PabloCastellano/libchamplain,StanciuMarius/Libchamplain-map-wrapping,GNOME/libchamplain,potyl/champlain,Distrotech/libchamplain