Rather than adding a canonicalised and non-canonicalised version of the
signal to `g_signal_key_bsa`, just add the canonicalised version. Signal
lookups always use the canonicalised key (since the previous commit).
This saves space in `g_signal_key_bsa`, which should speed up lookups;
and it saves significant space in the global `GQuark` table (a 9.6%
reduction in entries in that table, by a rough test using
gnome-software).
We have to be a little more relaxed on the signal name validation than
we are for property name validation, as GTK installs a
`-gtk-private-changed` signal which violates the signal naming rules.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
89f955db2d