Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20190714' into staging

Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20190714' into staging

Fixes for 3 tcg bugs

# gpg: Signature made Sun 14 Jul 2019 12:11:01 BST
# gpg:                using RSA key 7A481E78868B4DB6A85A05C064DF38E8AF7E215F
# gpg:                issuer "richard.henderson@linaro.org"
# gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>" [full]
# Primary key fingerprint: 7A48 1E78 868B 4DB6 A85A  05C0 64DF 38E8 AF7E 215F

* remotes/rth/tags/pull-tcg-20190714:
  tcg: Release mmap_lock on translation fault
  tcg: Remove duplicate #if !defined(CODE_ACCESS)
  tcg: Remove cpu_ld*_code_ra
  tcg: Introduce set/clear_helper_retaddr
  include/qemu/atomic.h: Add signal_barrier
  tcg/aarch64: Fix output of extract2 opcodes
  tcg: Fix constant folding of INDEX_op_extract2_i32

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