target/i386: Raise #GP on unaligned m128 accesses when required.

target/i386: Raise #GP on unaligned m128 accesses when required.

Many instructions which load/store 128-bit values are supposed to
raise #GP when the memory operand isn't 16-byte aligned. This includes:
 - Instructions explicitly requiring memory alignment (Exceptions Type 1
   in the "AVX and SSE Instruction Exception Specification" section of
   the SDM)
 - Legacy SSE instructions that load/store 128-bit values (Exceptions
   Types 2 and 4).

This change sets MO_ALIGN_16 on 128-bit memory accesses that require
16-byte alignment. It adds cpu_record_sigbus and cpu_do_unaligned_access
hooks that simulate a #GP exception in qemu-user and qemu-system,
respectively.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/217
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ricky Zhou <ricky@rzhou.org>
Message-Id: <20220830034816.57091-2-ricky@rzhou.org>
[Do not bother checking PREFIX_VEX, since AVX is not supported. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>