If sigsetjmp(3) is used, "gc_restart" must be of the correct type.

Signed-off-by: Peter Bex <peter.bex@xs4all.nl>
(cherry picked from commit 78c15c477f6109bc2f25281c9611c5bc96b13c74)
Additional jmpbuf fix
(cherry picked from commit 4e24ed510dd202850257fe63745796b9f639f86b)