Merge remote-tracking branch 'remotes/stsquad/tags/pull-more-fixes-150420-1' into...

Merge remote-tracking branch 'remotes/stsquad/tags/pull-more-fixes-150420-1' into staging

More small fixes for rc3

  - tweak docker FEATURE flags for document building
  - include sphinx configure check in config.log
  - disable PIE for Windows builds
  - fix /proc/self/stat handling
  - a number of gdbstub fixups following GByteArray conversion

# gpg: Signature made Wed 15 Apr 2020 11:38:56 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-more-fixes-150420-1:
  gdbstub: Introduce gdb_get_float32() to get 32-bit float registers
  gdbstub: Do not use memset() on GByteArray
  gdbstub: i386: Fix gdb_get_reg16() parameter to unbreak gdb
  target/m68k/helper: Fix m68k_fpu_gdb_get_reg() use of GByteArray
  linux-user: fix /proc/self/stat handling
  configure: disable PIE for Windows builds
  configure: redirect sphinx-build check to config.log
  tests/docker: add docs FEATURE flag and use for test-misc

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