1.0.4.13: refactor trap handling

 * All architectures had an essentially identical switch(trap){...}
   for different trap codes. Pull this into a single shared
   handle_trap function, which dispatches to architecture specific
   functions where necessary.

 * Remove unnecessary signal and siginfo arguments from breakpoint
   handling functions and interrupt_internal_error as a tentative step
   towards admitting that POSIX is not the only world out there.

 * Clean up some compiler warnings from the runtime, and a missing
   anti-copyright header.

 * Fix the PPC build... at least on G4 Darwin 10.3: no suseconds_t
   here.

 Tested on x86, x86-64, and PPC. Sparc, MIPS (and Alpha) testing
 needed.