Merge remote-tracking branch 'remotes/bonzini-gitlab/tags/for-upstream' into staging

* UI configury cleanups and Meson conversion
* scripts/gdb improvements
* WHPX cleanups and fixes
* cirrus win32 CI improvements
* meson gnutls workaround

# gpg: Signature made Tue 12 Jan 2021 16:05:19 GMT
# gpg:                using RSA key F13338574B662389866C7682BFFBD25F78C7AE83
# gpg:                issuer "pbonzini@redhat.com"
# gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>" [full]
# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>" [full]
# Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4  E2F7 7E15 100C CD36 69B1
#      Subkey fingerprint: F133 3857 4B66 2389 866C  7682 BFFB D25F 78C7 AE83

* remotes/bonzini-gitlab/tags/for-upstream:
  target/i386: Use X86Seg enum for segment registers
  configure: quote command line arguments in config.status
  configure: move Cocoa incompatibility checks to Meson
  configure: move GTK+ detection to Meson
  configure: move X11 detection to Meson
  gtk: remove CONFIG_GTK_GL
  cocoa: do not enable coreaudio automatically
  virtio-scsi: trace events
  meson: Propagate gnutls dependency
  Docs/RCU: Correct sample code of qatomic_rcu_set
  scripts/gdb: implement 'qemu bt'
  scripts/gdb: fix 'qemu coroutine' when users selects a non topmost stack frame
  meson: fix Cocoa option in summary
  whpx: move whpx_lapic_state from header to c file
  maintainers: Add me as Windows Hosted Continuous Integration maintainer
  cirrus/msys2: Cache msys2 mingw in a better way.
  cirrus/msys2: Exit powershell with $LastExitCode
  whpx: move internal definitions to whpx-internal.h
  whpx: rename whp-dispatch to whpx-internal.h
  meson: do not use CONFIG_VIRTFS

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