This patch simplifies the propagation of pointer shapes from
window-manager clients to the pointer. The "shape" report is routed to
the wm server, which, in turn, reports it to the pointer. This way, the
pointer can easily correlate the label of the application's "shape"
report with the label of the application's Nitpicker session. The
formerly used manual rewriting of the "shape" label is not needed
anymore.
Since the wm server provides a "Report" service now, its <provides>
declaration must cover "Report" in addition to "Nitpicker" to avoid
runtime error messages. Vice versa, the wm is now expected to request
"shape" reports, which should be routed to the pointer (using the
'label_last' routing attribute).
Fixes#3165
