Adds SYSENTER to the whitelist of supported hookable instructions in unicorn
as well as fixes up the existing sysenter_hook_x86 regression test which was
previously failing
Fixesunicorn-engine/unicorn#995
helper_sysenter in qemu/target-i386/seg_helper.c didn't check properly if a call interrupt callback was registred.
It has been fixed by copying the helper_syscall behavior.