Add code to use libusb-1.0 asynchronous transfers to fix problem of

occasional missed keys and eliminate use of key_timeout which disrupts the
main loop timing (by M. Jones).

configure.in

@@ -270,6 +270,29 @@ fi
 AC_SUBST(LIBUSB_LIBS)
 AC_SUBST(LIBUSB_CFLAGS)
 
+dnl ######################################################################
+dnl libusb-1.0 support
+dnl ######################################################################
+AC_MSG_CHECKING([if libusb-1-0 support has been enabled]);
+AC_ARG_ENABLE(libusb_1_0,
+	[AS_HELP_STRING([--disable-libusb-1-0],[disable USB support using libusb-1.0])],
+	[ if test "$enableval" != "no"; then
+		enable_libusb_1_0="yes"
+	fi ],
+	[ enable_libusb_1_0=yes ]
+)
+AC_MSG_RESULT($enable_libusb_1_0)
+
+if test "$enable_libusb_1_0" = "yes"; then
+	ifdef([PKG_CHECK_MODULES],
+		[PKG_CHECK_MODULES(LIBUSB_1_0, libusb-1.0 >= 1.0,
+			[AC_DEFINE(HAVE_LIBUSB_1_0, [1], [Define to 1 if you have libusb-1.0])],
+			[ enable_libusb_1_0=no ])],
+		[AC_MSG_WARN([pkg-config not (fully) installed; drivers requiring libusb-1.0 may not be built])])
+fi
+AC_SUBST(LIBUSB_1_0_LIBS)
+AC_SUBST(LIBUSB_1_0_CFLAGS)
+
 dnl ######################################################################
 dnl libftdi support
 dnl ######################################################################