Merge pull request #443 from kanoi/master

 Use mining start time for device MH/U calculations
compile unix code on Mac OS X
fixes not finding the config file in $HOME
ignore file that is generated on Macs
Create a pool_localgen bool function for testing when a pool can generate work locally.
Only show efficiency in pool information for pools that don't support local work generation.
Merge pull request #444 from zenwheel/master

Compile UNIX conditionals on Mac OS X
Create a usb_bulk_transfer wrapper for libusb_bulk_transfer to cope with pipe errors.
Differentiate libusb control transfer pipe errors from transfer errors since they're not fatal.
Add error message to libusb pipe error