mc.usb SLIP decode bug

[GoogleCodeExporter]

As reported by Andy Schmeder -

"In the SLIP decoder, when you encounter a SLIP_ESC character, you have to 
check the buffer 
position again before you dereference the next character because you might be 
at the end of the 
buffer. Currently, it crashes with a segmentation fault if a SLIP_ESC is the 
last character in the 
buffer.

To fix this you have to add a state variable to the object struct to track when 
the decoding state 
machine is in "escape mode" or not."

Original issue reported on code.google.com by lst...@gmail.com on 1 Jul 2009 at 5:13