Added missing usb_strerror function.

src/main/c/src/USB.c

@@ -344,3 +344,16 @@ JNIEXPORT jint JNICALL METHOD_NAME(USB, usb_1interrupt_1read)
     return usb_interrupt_read(unwrap_usb_dev_handle(env, handle),
         ep, buf, buflen, timeout);
 }
+
+
+/**
+ * string usb_strerror()
+ */
+
+JNIEXPORT jstring JNICALL METHOD_NAME(USB, usb_1strerror)
+(
+    JNIEnv *env, jclass class
+)
+{
+    return (*env)->NewStringUTF(env, usb_strerror());
+}

src/main/java/de/ailis/usb4java/USB.java

@@ -755,4 +755,13 @@ public final class USB
 
     public static native int usb_interrupt_read(final USB_Dev_Handle handle,
         final int ep, final ByteBuffer bytes, final int timeout);
+
+
+    /**
+     * Returns the last error message.
+     *
+     * @return The last error message.
+     */
+
+    public static native String usb_strerror();
 }