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/tests/test-capture-cursor.c

@@ -22,13 +22,13 @@
 #include <glib/gstdio.h>
 #include <sysprof-capture.h>
 
-static gboolean
+static bool
 increment (const SysprofCaptureFrame *frame,
-           gpointer              user_data)
+           void                      *user_data)
 {
   gint *count= user_data;
   (*count)++;
-  return TRUE;
+  return true;
 }
 
 static void