Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20180316' into staging

Queued TCG patches

# gpg: Signature made Thu 15 Mar 2018 17:17:31 GMT
# gpg:                using RSA key 64DF38E8AF7E215F
# gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>"
# Primary key fingerprint: 7A48 1E78 868B 4DB6 A85A  05C0 64DF 38E8 AF7E 215F

* remotes/rth/tags/pull-tcg-20180316:
  tcg: Add choose_vector_size
  tcg/i386: Support INDEX_op_dup2_vec for -m32
  tcg: Improve tcg_gen_muli_i32/i64

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>