traps, and interrupts The earlier (4.4bsd) code didn't do the first two, and
got the last one wrong. Also print some functions (e.g., trap handlers)
by name. Add hook to use something other than printf() as the output
function, e.g,. for kernel debugging.
Tested with the `native' toolset, but not ELF format kernels.
(i.e., unwinding the $GP register is not tested.)
The stack backtrace code that interprets and unwinds stackframes is still
opaque and stylistically awkward.
fb9f07db36