After the recent changes we only have a single implementation of
QSlotObjectBase, which can handle free functions, member functions,
functors, and lambdas. Rename it to callable, and explicitly hide
the static implementation function so that it doesn't become a symbol
of static libraries using Qt.
Also rename makeSlotObject to makeCallableObject, and polish coding
style and comments in the qobjectdefs_impl header a bit.
Change-Id: Id19107cedfe9c624f807cd8089beb80e9eb99f50
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
ccd3b28aab