kvm: decode the argument of KVM_{SET, GET}_SREGS ioctl command

kvm: decode the argument of KVM_{SET, GET}_SREGS ioctl command

* configure.ac (AC_CHECK_TYPES): Add struct kvm_sregs.
* kvm.c [HAVE_STRUCT_KVM_SREGS] (kvm_ioctl_decode_sregs): New function.
(kvm_ioctl) [HAVE_STRUCT_KVM_SREGS] <KVM_SET_SREGS, KVM_GET_SREGS>:
Use it.
* linux/arch_kvm.c (arch_print_kvm_sregs): New function.
* linux/x86_64/arch_kvm.c (PRINT_FIELD_KVM_SREGS_STRUCT): New macro.
(kvm_ioctl_decode_regs_dtable, kvm_ioctl_decode_regs_segment,
arch_print_kvm_sregs): New functions.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>