Externals: Update libusb to 1.0.23-rc1

Now has support for isochronous transfers in the WinUSB backend,
which may or may not work better than the UsbDk backend.

Externals/libusb/Makefile.am

@@ -0,0 +1,28 @@
+AUTOMAKE_OPTIONS = dist-bzip2 no-dist-gzip
+ACLOCAL_AMFLAGS = -I m4
+DISTCLEANFILES = libusb-1.0.pc
+EXTRA_DIST = TODO PORTING msvc libusb/libusb-1.0.def libusb/version_nano.h \
+  examples/getopt/getopt.c examples/getopt/getopt1.c examples/getopt/getopt.h \
+  android Xcode
+SUBDIRS = libusb doc
+
+if BUILD_EXAMPLES
+SUBDIRS += examples
+endif
+
+if BUILD_TESTS
+SUBDIRS += tests
+endif
+
+pkgconfigdir=$(libdir)/pkgconfig
+pkgconfig_DATA=libusb-1.0.pc
+
+.PHONY: dist-up
+
+reldir = .release/$(distdir)
+dist-up: dist
+	rm -rf $(reldir)
+	mkdir -p $(reldir)
+	cp $(distdir).tar.bz2 $(reldir)
+	rsync -rv $(reldir) frs.sourceforge.net:/home/frs/project/l/li/libusb/libusb-1.0/
+	rm -rf $(reldir)