Merge remote-tracking branch 'remotes/rth-gitlab/tags/pull-cap-20201003' into staging

Merge remote-tracking branch 'remotes/rth-gitlab/tags/pull-cap-20201003' into staging

Update capstone submodule from v3.0.5 to v5 ("next").
Convert submodule build to meson.
Enable capstone disassembly for s390x.
Code cleanups in disas.c

# gpg: Signature made Sat 03 Oct 2020 10:33:44 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-gitlab/tags/pull-cap-20201003:
  disas/capstone: Add skipdata hook for s390x
  disas: Enable capstone disassembly for s390x
  disas: Split out capstone code to disas/capstone.c
  disas: Configure capstone for aarch64 host without libvixl
  disas: Cleanup plugin_disas
  disas: Use qemu/bswap.h for bfd endian loads
  disas: Clean up CPUDebug initialization
  disas: Move host asm annotations to tb_gen_code
  capstone: Require version 4.0 from a system library
  capstone: Update to upstream "next" branch
  capstone: Convert Makefile bits to meson bits

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