a smaller bootloader.

[smaller09]

hi pascal,
The flash is limited. so I just try to reconstruct a smaller bootloader for the MPM project.
the code is here
https://github.com/smaller09/bootloader
and it just a rewrite of the StmMultiBoot
the bin size is 3776 bytes
I had tested it with avrdude to verify that the bootloader is working fine with stm32f103cbt6 bull pill.
would u please take a look.

PS: for more flash room. I have another version (omit the support for usart1, I think that's ok for internal module) is about 1.8K.
PS2: I had updated the code, it's now 2032 bytes (with usart1 and led), need test.