Win32 has a gdk_test_simulate_key() implementation since GTK+ 2.24.25.

See bug 734879: commits c87c5cd in GTK+ master, and 03c5335 in gtk-2-24
branch.
app: add GimpOperationScalarMultiply

which multiplies each float in a gegl_format_n(float, n) input
by a factor.