Merge branch 'wip/libusb-1.0' of http://gnuradio.org/git/jcorgan into master

This merge adds support for libusb1.0 in the usrp component.  To enable,
you must add --with-fusb-tech=libusb1 to your configure command line.

Existing support for libusb0.1 is retained, no changes are needed.

Most of the work was done here by Thomas Tsou.

* 'wip/libusb-1.0' of http://gnuradio.org/git/jcorgan: (32 commits)
  Cleanup in preparation for merge
  Add required include directory for new header organization
  Added config.h headers to fix win32 build
  Consolidate conditional headers into libusb_types.h, use automake
  Change write_internal_ram in usrp_prims to print signed error code
  Allow fusb_sysconfig to build on non-linux libusb-0.12 impls
  Comments for usrp_prims
  Removed internal functions from external header file
  Moved to single generated fusb.h, headers now generated out of lib directory
  Added copyright header
  Removed preprocessor declrs out of fusb.h and created separate fusb_libusb1_base.h
  Fixed libusb1 configure bug, libusb1 updates for previous usrp_prims integration
  Commonized more usrp_prims code and renamed libusb-0.12 files to libusb0
  Fixed bug usb_control_transfer bug
  Combined additiona usrp_prims code
  Fix glitch from previous commit
  changes to build on windows / cygwin
  Re-added non pkgconfig support for libusb
  Autoconf support for checking the required version of libusb based on fusb-tech
  Use default arguments instead of overloaded virtual constructors for cleaner interface
  ...