Core: Fix a Clang warning in io.c

* Using sizeof() in the UNUSED() macro didn't silence all
  unused variable warnings.
* Also fix an "unused ctx" warning when ENABLE_DEBUG_LOGGING is on
* Also improve debug output on libusb_open() failure
Core: Improve instrumentation of timerfd_settime failures

* Report errno as well as itimerspec data
* Also reuse the timeout variable set to &transfer->timeout
Samples: Make target mandatory with -b option in xusb
Windows: Fix C4005 warning under VS2012 for inline.

* Changed inline macro to not fire when using Visual Studio/C++,
  which attempts to redefine the macro - resulting in a C4005 warning.
Windows: Add libusbk.sys & libusb0.sys driver support

* Both libusbk and libusb0.sys rely on libusbk.dll being
  installed to provides a WinUSB-like API for driver access.
* In case libusbk.dll is not present, fall back to WinUSB.
* Closes #11
* Closes #12
Windows: Add support for 2nd gen Renesas USB 3.0 controllers

* Driver version 3.0.20.0 for uPD720201 & uPD720202 uses RUSB3HUB
* Closes #40
Misc: Update and shorten various libusbx URLs
Core: Handle >= 1 second transfer timeout in libusb_submit_transfer()

* Comparisons between tv_nsec and 1 sec should be >= rather than >,
  as we can end up in situations where tv_nsec is exactly 1000000000,
  which calls such as timerfd_create() do not accept.
* Issue reported by Sebastian K. See:
  https://sourceforge.net/mailarchive/message.php?msg_id=29706972
Linux: Add support for the new get_capabilities ioctl

* There were a few (new) usbdevfs capabilities which libusbx could not
  discover in any other way then checking the kernel version.
* However, this presents the following problems:
  1) It is just not very pretty
  2) Given the tendency of enterprise distros to backport stuff it is not
     reliable
  3) Some of these features turn out to not work with certain host controllers,
     making depending on them based on the kernel version not a good idea
* Therefore a new USBDEVFS_GET_CAPABILITIES ioctl has been added to the kernel
  to offer a better way to find out a device's capabilities (technically
  the capabilities of the host controller to which the device is attached,
  but that does not matter).
Linux: Avoid unnecessary splitting of bulk transfers

* With the latest kernels it is no longer needed to always split large bulk
  transfers into multiple urbs. This patch takes advantage of this by not
  splitting when not necessary. Note that the non-split code path is in essence
  using the old split code path with an urb count which is always 1.
* This leads to more sane handling of large transfers with recent kernels,
  although our splitting code is well tested, not splitting at all still is
  a lot better :)
* When used with a recent kernel, this also fixes the problems, on XHCI attached
  devices, when a large bulk-in transfer ends with a short read in an urb other
  then the last urb.
* For more on this see: http://marc.info/?l=linux-usb&m=133797554910355
Linux: Return ERROR_NOT_FOUND in detach-kernel-driver if usbfs is already bound

* Currently applications for devices which only are accessed from userspace
  can use claim / release interface to make sure they don't get in each others
  way.
* The same however does not work for applications which first need to detach
  a "native" / in kernel driver, as this detach will not only detach native
  drivers but also the usbfs driver, thus stealing the device from another
  userspace / libusbx app.
* This patch fixes libusb_detach_kernel_driver to only detach "real" kernel
  drivers and not the special usbfs driver used for userspace access to
  USB devices. If the usbfs driver is found LIBUSB_ERROR_NOT_FOUND will be
  returned to indicate no driver was detached.
Windows: Suppress unwanted error message on filter driver

* Interface access error message was unconditional, even if the
  filter driver was found later on.
Samples: xusb improvements

* update and fix usage details
* make topology and speed printout optional (option -i)
* remove unneeded option -g
Windows: Fix handling of composite devices

* Pass missing sub_api parameter to set_composite_interface() and
  composite_submit_control_transfer()
* Remove api_flags attribute, that cannot apply for multiple interfaces
* Also simplifies the internal ENUM_DEBUG mode
* Also move polluting info logging message to debug
Doc: Update logging documentation regarding stderr usage
All: Avoid polluting errors reported on device disconnect

* Makes libusb_cancel_transfer not log an error when the cancel fails
  with LIBUSB_ERROR_NO_DEVICE, so that apps can properly clean things
  up on device disconnect without flooding the console with these errors.
* Also, some devices (Cypress FX) may switch VID:PID on the fly during
  firmware upload => reduce severity of the Windows message when that happens.
Samples: Add fxload sample for Cypress EZ-USB chips

* This program was modified from the original fxload at:
  http://linux-hotplug.sourceforge.net to add libusbx
  as well as non HEX images support.
* Only supports RAM upload for now, with EEPROM and FX3
  support to be added at a later stage.
Windows: Switch to ALLOW_PARTIAL_READS pipe policy enabled by default

* This avoids an issue when libusbK is used for bulk transfers, which
  is most likely due to a libusbK bug
* See https://sourceforge.net/mailarchive/message.php?msg_id=29736015
Samples: Display VID:PID of the tested device in xusb

* Also amend the wording of the "no option" comment.
* Closes #42
Core: Update libusb.h header in accordance with the latest USB specs

* IMPORTANT: This update fixes a typo in the API where MaxPower was being
  used instead of bMaxPower, with the latter being what is actually in
  the specs.
* As a result, applications that were using MaxPower need to be updated
  for bMaxPower.
* If you must maintain compatibility with libusb or older versions of
  libusbx, you may also want to either use a #define or copy/paste
  struct libusb_config_descriptor from libusb.h under a new name, and
  then use a cast on calls that require it. For more info, see the
  1.0.13 release notes in the NEWS file.
* Also update copyright notice