Attached is a patch to add the case for interrupting the gdbstub and 
sending the correct signal to gdb.

The gdb serial protocol states that if you interrupt the stub with a 
"control-c" in gdb that it should stop with S02 (SIGINT) to indicate 
that it was interrupted.   I also added the tlb flush so that 
breakpoints can be written in correctly.  I found that if I ran a 
pentium qemu instance and broke in with gdb and planted a breakpoint at 
do_fork() that it was not immediately hit due to the lack of the 
flush.   With the patch, it reliably stops all the time now when a 
breakpoint is planted after interrupting the stub.

Thanks,
Jason.