This is required to be able to move objects that inherit from it.
(Note that this patch also #ifs out the class for the externals that
include it yet are compiled in pre-C++11 mode. It shouldn't matter,
since those externals don't use it.)
- Make "copy data into bundle" depend on the files actually being
changed, rather than being run on every build.
- postprocess_bundle depends on system files and checking the Dolphin
binary and all that, and would be iffy to try to avoid rerunning;
but it's only needed to produce a redistributable bundle, so add
SKIP_POSTPROCESS_BUNDLE to skip it for development.