[CVS ci] resumable exception

[Leopold Toetsch]

I've checked in a first attempt towards resumable exceptions thrown at 
opcode level. s. t/op/hacks_4 for an example.

As such ops have to be marked as branches, I did extend OpsFile.pm to 
understand:

  restart ADDRESS(resume);

This marks such opcode as branches. s. var.ops: find_lex_p_s.

internal_exception() is replaced by real_exception() which takes 2 more 
arguments (interpreter, resume_addr). This for now doesn't longjmp to 
the handler (which it probably should do) but branches directly there by 
returning the handler address.

Comments welcome,
leo