Update the offsets used to save registers into the stejmp jmp_buf
structure in order to:
* Avoid writing the supervision register outside the buffer and thus
clobbering something on the stack. Previously the supervision register
was written at offset 124 while the buffer was of length 124.
* Shrink the jmp_buf down to the size actually needed, by avoiding holes
at the locations of omitted registers.
Invert equality check instruction to correct the return value handling
in longjmp.
The return value should be the value of the second argument to longjmp,
unless the argument value was 0 in which case it should be 1.
Previously, longjmp would set return value 1 if the second argument was
non-zero, and 0 if it was 0, which was incorrect.
Martin Erik Werner
Jeff Johnston
Corinna Vinschen