PR# 13722 Compiler dies with seg fault when trying to report stack initialization failure

Do "limit datasize 1024" (csh) to limit data segment to 1024 KB.
Run compiler.  Compiler dies with a panic due to failure to create
the runtime stacks (which is fine) but then gets a seg fault when
trying to display the stack trace.  Output is:

   ec: PANIC: can't create runtime stacks ...

   ec: system execution failed.
   Following is the set of recorded exceptions.
   NB: The raised panic may have induced completely inconsistent information:

   Segmentation fault

Looks like the problem is that `esfail' (in except.c) needs to skip calling
`backtrack' (which calls `extop', which doesn't work when eif_stack is
not initialized) if eif_stack.st_cur or eif_stack.st_top is NULL.
Don't know if call to `dump_trace_stack' will also fail in this situation.