Fixes and optimizations to USBHDFSD:
1. Fixed file locking, which prevents a file from being opened multiple times for writing. File locking is now done based on the file's starting cluster number.
2. Optimized the code by declaring internal functions and structures as static. I've also cut out unused code.
3. Completed the rename function, which is accessed via IOCTL. Refer to common/include/usbhdfsd.h for details.
4. Fixed line identation in various files.