Bug#712076: liblouis: Should build-dep on python/3-all vice python/3-all-dev
liblouis doesn't actually use the python development headers to build, so the
build-dep on the -dev packages isn't needed. This isn't actively harmful
other than the minor effect of needing more packages installed to build. It
does, however, make liblouis show up on the python3.3 transition tracker when,
in fact, it does not need to make any changes for the transition.