libc: mips: Fix setjmp/longjmp for MIPS64 N64 ABI

libc: mips: Fix setjmp/longjmp for MIPS64 N64 ABI

When booting a Linux system with qemu-system-mips64 the execution
of $(pwd) in the ash shell triggers a segmentation fault. Ash uses
setjmp/longjmp for exception handling.

After looking at the glibc implementation,
I found some differences, with this patch tries to resolve.
Now the system boots up fine and no segmentation faults occur.

The global pointer should be restored and the types for the
register values should be wide enough.

See:
http://www.cygwin.com/ml/libc-alpha/2003-03/msg00363.html

Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>