Merge remote-tracking branch 'remotes/kraxel/tags/modules-20201022-pull-request' into staging

modules: build spice and opengl as module.

# gpg: Signature made Thu 22 Oct 2020 06:12:03 BST
# gpg:                using RSA key 4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>" [full]
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>" [full]
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>" [full]
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/modules-20201022-pull-request:
  opengl: build opengl helper code modular
  opengl: build egl-headless display modular
  spice: flip modules switch
  modules: add spice dependencies
  modules: dependencies infrastructure
  spice: load module when enabled on the cmdline
  spice: wire up monitor in QemuSpiceOps.
  spice: move display_add_client() to QemuSpiceOps.
  spice: move auth functions to QemuSpiceOps.
  spice: move add_interface() to QemuSpiceOps.
  spice: move display_init() to QemuSpiceOps.
  spice: move qemu_spice_init() to QemuSpiceOps.
  spice: add QemuSpiceOps, move migrate_info
  spice: add module helpers

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