Fix for circular references detection in almost all cases, fixing https://bugs.launchpad.net/inkscape/+bug/167247 and a few of its duplicates. This fix is aimed at preventing any sort of circular references with the URIReference::_acceptObject method, checking the absence of loops in the reference+child tree. There can be some performance improvements done if we add a pointer from cloned sub-objects to their origin sub-object. The remaining cases that are not fixed can involve non-trivial loops using one or more "url()" stylesheet references. Being able to take them into account would require a non-obvious style.cpp refactoring making use of URIReference for this kind of reference (and not handling manually the signals in the styling code, which would probably be a good thing to do anyway)

Finished cleanup of outdated SP_OBJECT_REPR C macro.

Super duper mega (fun!) commit: replaced encoding=utf-8 with fileencoding=utf-8 in all 1074 Vim modelines. The reason for this is that (a) setting the encoding isn't nice, and (b) Vim 7.3 (with modeline enabled) disallows it and pops up an error whenever you open any file with it ("invalid modeline"). Also corrected five deviant modestrings: * src/ui/widget/dock.cpp and src/ui/widget/dock.h: missing colon at the end * src/ui/dialog/tile.cpp: removed gratuitous second colon at the end * src/helper/units-test.h: removed gratuitous space before a colon * share/extensions/export_gimp_palette.py: missing textwidth=99 That's my geekiest commit yet.

Clean up comments and remove (already commented) debugging messages

Warning cleanup

Fundamentally reworked version of the 3D box tool (among many other things, this fixes bugs #168900 and #168868). See mailing list for details. Sorry for this single large commit but it was unfeasible to keep the history.