In gimp_tool_compass_update_angle(), use fuzzy comparisson when
determining whether to update the angle properties, to avoid
infinite recursion due to floating-point inaccuracies.  In
partcicular, on x86, when using the x87 FPU rather than SSE, the
floating-point registers are 80-bit, while the properties are
stored as 64-bit, which can create small discrepancies between the
calculated angles and the stored values.