#546 AVX2 bugs

[A Fog]

Thank you for adding AVX2 support to NASM. I have now added AVX2 to my disassembler at www.agner.org/optimize/objconv.zip and NASM has been very useful for testing it (30 July 2011 snapshot, Windows version, nasm -O9 -f win64).

The following AVX2 instructions failed to assemble:
vpmovsxbw ymm1,xmm2 ; error: invalid combination of opcode and operands
vpsllw ymm1,ymm2,3 ; error: invalid effective address
vpslld ymm1,ymm2,3 ; error invalid effective address
vpsllq ymm1,ymm2,3 ; nasm warning sometimes: warning: byte value exceeds bounds. Makes misplaced relocation record
vpsrld ymm1,ymm2,3 ; error: invalid effective address
vpsrad ymm1,ymm2,3 ; error: invalid effective address
vpermq ymm1,[rsi],9 ; error: parser: instruction expected

[Cyrill Gorcunov]

Thanks a huge for report! I'll take a look as only time permits.

[Nobody/Anonymous]

We had a typo with "vpermq" (was defined as "vpermpq"), I've just fixed it but not pushed out yet. Other errors need more time for investigation.