Various testing updates

  - semihosting re-factor (used in system tests)
  - aarch64 and alpha system tests
  - editorconfig tweak for .S
  - some docker image updates
  - iotests clean-up (without make check inclusion)

# gpg: Signature made Tue 28 May 2019 17:26:34 BST
# gpg:                using RSA key 6685AE99E75167BCAFC8DF35FBD0DB095A9E2A44
# gpg: Good signature from "Alex Bennée (Master Work Key) <alex.bennee@linaro.org>" [full]
# Primary key fingerprint: 6685 AE99 E751 67BC AFC8  DF35 FBD0 DB09 5A9E 2A44

* remotes/stsquad/tags/pull-testing-next-280519-2: (27 commits)
  tests/qemu-iotests: re-format output to for make check-block
  tests/qemu-iotests/group: Re-use the "auto" group for tests that can always run
  Makefile.target: support per-target coverage reports
  Makefile: include per-target build directories in coverage report
  Makefile: fix coverage-report reference to BUILD_DIR
  .travis.yml: enable aarch64-softmmu and alpha-softmmu tcg tests
  tests/tcg/alpha: add system boot.S
  tests/tcg/multiarch: expand system memory test to cover more
  tests/tcg/minilib: support %c format char
  tests/tcg/multiarch: move the system memory test
  tests/tcg/aarch64: add system boot.S
  editorconfig: add settings for .s/.S files
  tests/tcg/multiarch: add hello world system test
  tests/tcg/multiarch: add support for multiarch system tests
  tests/docker: Test more components on the Fedora default image
  tests/docker: add ubuntu 18.04
  MAINTAINERS: update for semihostings new home
  target/mips: convert UHI_plog to use common semihosting code
  target/mips: only build mips-semi for softmmu
  target/arm: correct return values for WRITE/READ in arm-semi
  ...

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