Log Message:
update to libusb-1.0.20
add experimental SunOS backend support adapted from the upstream RTI
submission from Oracle and initial illumos support from OpenIndiana/Hipster

From the Changelog:
For detailed information about the changes below, please see the git log or
visit: http://log.libusb.info

2015-09-13: v1.0.20
* Add Haiku support
* Fix multiple memory and resource leaks (#16, #52, #76, #81)
* Fix possible deadlock when executing transfer callback
* New libusb_free_pollfds() API
* Darwin: Fix devices not being detected on OS X 10.8 (#48)
* Linux: Allow larger isochronous transfer submission (#23)
* Windows: Fix broken builds Cygwin/MinGW builds and compiler warnings
* Windows: Fix broken bus number lookup
* Windows: Improve submission of control requests for composite devices
* Examples: Add two-stage load support to fxload (#12)
* Correctly report cancellations due to timeouts
* Improve efficiency of event handling
* Improve speed of transfer submission in multi-threaded environments
* Various other bug fixes and improvements
The (#xx) numbers are libusb issue numbers, see ie:
https://github.com/libusb/libusb/issues/16

MAKE_JOBS_SAFE=no given build issues when enabled.