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/travis-autogen.sh

@@ -0,0 +1,39 @@
+#!/bin/bash
+
+# Warnings enabled
+CFLAGS="-Wall -Wextra"
+
+CFLAGS+=" -Wbad-function-cast"
+#CFLAGS+=" -Wcast-align"
+CFLAGS+=" -Wchar-subscripts"
+CFLAGS+=" -Wempty-body"
+CFLAGS+=" -Wformat"
+CFLAGS+=" -Wformat-security"
+CFLAGS+=" -Winit-self"
+CFLAGS+=" -Winline"
+CFLAGS+=" -Wmissing-declarations"
+CFLAGS+=" -Wmissing-include-dirs"
+CFLAGS+=" -Wmissing-prototypes"
+CFLAGS+=" -Wnested-externs"
+CFLAGS+=" -Wold-style-definition"
+CFLAGS+=" -Wpointer-arith"
+CFLAGS+=" -Wredundant-decls"
+CFLAGS+=" -Wshadow"
+CFLAGS+=" -Wstrict-prototypes"
+CFLAGS+=" -Wswitch-enum"
+CFLAGS+=" -Wundef"
+CFLAGS+=" -Wuninitialized"
+CFLAGS+=" -Wunused"
+CFLAGS+=" -Wwrite-strings"
+
+# warnings disabled on purpose
+CFLAGS+=" -Wno-unused-parameter"
+CFLAGS+=" -Wno-unused-function"
+CFLAGS+=" -Wno-deprecated-declarations"
+
+# should be removed and the code fixed
+CFLAGS+=" -Wno-incompatible-pointer-types-discards-qualifiers"
+
+export CFLAGS
+
+./autogen.sh "$@"