***** µCFAT *****
This is a small-ish implementation of FAT16/32.
It is intended for microcontrollers with a limited amount
of RAM. Thus, performance has been sacrificed for a smaller 
memory footprint where possible. As a result, about a kB is the
minimum amount of RAM needed to use µCFAT, although you'll need
more than that to really do anything with the data you load.
It was specifically written to be used on an LPC1114 cortex M0
microcontroller, however, no microcontroller specific features are
used. It has two hooks, read_sector() and write_sector() that you
modify to use your block device code (ie. SD card code.)

You also need to give it a buffer the size of one sector
(512 Bytes,) which you provide by setting the global pointer
sector_buff. The contents of this buffer is only defined
after a read operation, all other calls will trash it with
temporary data.

Before any operations can be done, fat_init() must be called.
If any read/write errors are encountered, fat_init() will need
to be called again. This will invalidate all open file descriptors.
A failing read/write can be used to implement basic hot-swap support,
as the new media will not be initialized on an interface level.

If a read/write error was encountered that resulted in the last
error, fat_valid() will return false.

Requirements:
	* A C99 compatible C compiler (stdint, stdbool are used)
	* At least 1 kB of µC RAM
	* An interface for reading/writing sectors
	* About 4 kB of available ROM for fat.c (compiled with -Os, THUMB)

Features:
	* Provides an interface for basic FS operation
	* Read files (a sector at a time)
	* Write files (a sector at a time)
	* Seek in files (in sector increments)
	* Create/delete files/folders
		- To create a folder, use file attribute 0x10
		- Only empty folders can be deleted
	* Set filesizes to a non sector-aligned number
	* List the contents of a directory


Limitations:
	* Only per sector read/write/seek
	* No long file names, only 8.3 supported
	* Only supports 512 byte sectors.
	* Only one sector can be read/written at a time
	* Filesystem is case sensitive
	* No checks are done for illegal characters in filenames
	* A fixed maximum of open files (configurable with a #define)
	* Does not support partition tables

Protip: Compile fat.c with -Os, or the object file will be very large.
For gcc targeting LPC1114, -O3 will produce a 14 kB object file, while
-Os produces a 4 kB object file. Since speed will be crap anyway, this
shouldn't be a big sacrifice. There doesn't seem to be as big of a
difference on x86 (larger binary,) so your milage may vary.

Provided is apart from the actual implementation (fat.c) also a demo
program in test.c, which will do some basic file operations on the
file system image given to main in argv[1].