libsysprof-capture: Use stdbool instead of gboolean

Another step towards dropping GLib as a dependency of
libsysprof-capture.

Unlike the previous commit which replaced GLib integer types with the
bitwise equivalent C standard types, `stdbool` is potentially a different
width from `gboolean`, so this is an ABI break.

It therefore involves some changes to callback functions in the tests
and tools, and in libsysprof.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Helps: #40

src/libsysprof/sysprof-control-source.c

@@ -123,10 +123,10 @@ sysprof_control_source_init (SysprofControlSource *self)
   g_array_set_clear_func (self->source_ids, remove_source_id);
 }
 
-static gboolean
-event_frame_cb (gconstpointer  data,
-                gsize         *length,
-                gpointer       user_data)
+static bool
+event_frame_cb (const void *data,
+                size_t     *length,
+                void       *user_data)
 {
   const SysprofCaptureFrame *fr = data;
   RingData *rd = user_data;