MFC r361977: libusb: improve compatibility
Specifically, add LIBUSB_CLASS_PHYSICAL and the libusb_has_capability API.
Descriptions and functionality for these derived from the
documentation at [0]. The current set of capabilities are all supported by
libusb.
These were detected as missing after updating net/freerdp to 2.1.1, which
attempted to use both.
[0] http://libusb.sourceforge.net/api-1.0/group__libusb__misc.html
git-svn-id: svn://svn.freebsd.org/base/stable/10@362224
ccf9f872-aa2e-dd11-9fc8-
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