SmartBOB-USB plug-in updated to version 0.46.221 (fixes bugs from prev release)

[Steve Stallings]

The Mach4Hobby plugin for the SmartBOB-USB family of controllers has been updated to version 0.46.221,
released 31 August 2016.  This plug-in requires Mach4 builds 2872 or higher. It has been tested with builds
2872 and 2914, and should work with later builds when released.

Full details of this release are here: http://www.pmdx.com/Downloads_/ReleaseNotes_Ver_0_46_221.html

Download the plug-in here:  http://www.pmdx.com/PMDX-SmartBOB-USB-Plug-In

Major changes for this release (see the release notes for a complete list of changes):

(1) Fixes bugs introduced by spindle control enhancements in previous release. Interactions
      with encoder support and spindle speed reporting on some models of SmartBOB.

(2) Turn off Steps LED when errors halt motion.

(3) Do not allow "Expanded Input" mode on the PMDX-416 which has its own isolated
      inputs and does not support inputs on the ribbon header.

(4) Prevent Index input events from flooding Debug logs.