Wrap ChamplainMapSourceChain

	* champlain/champlainmm.h: Add map-source-chain.h.
	* champlain/champlainmm/.gitignore: Ignore map-source-chain.*.
	* champlain/src/filelist.am: Add map-source-chain.hg.
	* champlain/src/map-source-chain.[hg|ccg]: New files.
	* tools/extradefs/generate_extra_defs_libchamplain.cc: Add
	CHAMPLAIN_TYPE_MAP_SOURCE_CHAIN.