Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20180502' into staging

Queued TCG patches

# gpg: Signature made Wed 02 May 2018 18:43:33 BST
# 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-20180502:
  tcg: workaround branch instruction overflow in tcg_out_qemu_ld/st
  tcg: Improve TCGv_ptr support
  tcg: Allow wider vectors for cmp and mul
  tcg/arm: Fix memory barrier encoding
  tcg: Document INDEX_mul[us]h_*

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