With this patch the 'GNU Project Debugger' (GDB) can be built for Noux.
The included run script connects GDB and GDB monitor via a cross-link
terminal and allows interactive source-level debugging of the GDB monitor
test application on Genode.
Fixes#280.
The patch fixes a corner-case problem with using the two-byte 'INT 0'
instruction for breakpoints. The fix changes the breakpoint instruction
to the single-byte 'HLT'. 'HLT' is a privileged instruction and triggers
an exception when executed in user mode. Patch by Christian Prochaska.