Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20171115' into staging

User-mode memory helper fixes

# gpg: Signature made Wed 15 Nov 2017 12:32:33 GMT
# gpg:                using RSA key 0x64DF38E8AF7E215F
# 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-20171115:
  target/arm: Fix GETPC usage in do_paired_cmpxchg64_l/be
  target/arm: Use helper_retaddr in stxp helpers
  tcg: Record code_gen_buffer address for user-only memory helpers

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