Good work. But it might be easier to just download the malloc.c file from the 1.7.0 release and add it to any program that needs it (I'm guessing not many programs will use malloc() given how little RAM is available):http://svn.savannah.nongnu.org/viewvc/
This will require fewer (well...none) changes to user code and when the AVR-LIBC version catches up in the Arduino software the malloc.c files can just be dropped from user programs.
The Rugged Motor Driver
: two H-bridges, more power than an L298, fully protected