Fix try/catch on ARM

When returning _to_ tryWrapper we pass the address on where to continue
execution in r0. So in our leaveStackFrame() we shouldn't clobber r0
and in fact there's little value in restoring r0-r3 given that they're
used to pass arguments and don't require save/restore.

Change-Id: Iba0091e19eb74347472e698ffc7687e647a5e5be
Reviewed-by: Lars Knoll <lars.knoll@digia.com>