nx-X11/programs/Xserver/hw/nxagent/Display.c: use new ReconnectTolerance nxagentOption in nxagentCheckForDefaultDepthCompatibility() and modify behavior based on this value.

Recognized values:
  - Strict means that the old and new default depth values
    must match exactly.
  - Safe or Risky means that the default depth values
    might differ, but the new default depth value must be at
    least as high as the former default depth value. This is
    recommended, because it allows clients with a
    higher default depth value to still connect, but
    not lose functionality.
  - Bypass or higher means that all of these checks are
    essentially deactivated. This is probably a very
    bad idea.

Note that the default ReconnectTolerance value is still Strict.