Fix trap_handler so that the saved_* parameters are set up correctly

Fix trap_handler so that the saved_* parameters are set up correctly
before invoking trap_recover.  This fixes the bug by which all traps
were reported as "User microcode reset".

Add find_signal_code_name to generate a string for the signal code
using DECLARE_UX_SIGNAL_CODES defined in uxtrap.h .

Modify setup_trap_frame to use find_signal_code_name .

Fix find_block_address_in_area to not run into an infinite loop (it
was not incrementing the area pointer on most objects).