Wrap ChamplainFileTileSource

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