Expose transform tools when in weight paint mode with pose-mode enabled,
displaying transform tools in the toolbar, as is already done in
object & pose mode.
These are only shown when weight-paint + pose mode are active at once.
This allows single key-strokes to activate tools, needed when
tool-access is set as the default action for G/R/S key bindings.
Reviewed By: JulienKaspar
Ref D13028
b3597f310d