Log Message:
Update to 1.6:

 o Removed the hard dependancy on openjade or jade, since XML is used mainly
   now rather than SGML.
 o Install the .pc file in $(datadir) rather than $(libdir) since gtk-doc is
   architecture-independant.
 o Added "--ignore-decorators" option to ignore a list of declarators in
   function declarations.
 o Support '#Object::signal'/'#Object:property' to link to signals/properties
 o Fixed missing index terms.