Makefile.PL tweaks
Makefile.PL tweaks

Various fixes to the Makefile.PL:

  - change the dependencies to be conditional
  - install the champlain-perl.h header file
  - check dependencies first, then invoke ExtUtils::Depends

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