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

* Reverse debugging (Pavel)
* CFLAGS cleanup (Paolo)
* ASLR fix (Mark)
* cpus.c refactoring (Claudio)

# gpg: Signature made Tue 06 Oct 2020 07:35:09 BST
# 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: (37 commits)
  tests/acceptance: add reverse debugging test
  replay: create temporary snapshot at debugger connection
  replay: describe reverse debugging in docs/replay.txt
  gdbstub: add reverse continue support in replay mode
  gdbstub: add reverse step support in replay mode
  replay: flush rr queue before loading the vmstate
  replay: implement replay-seek command
  replay: introduce breakpoint at the specified step
  replay: introduce info hmp/qmp command
  qapi: introduce replay.json for record/replay-related stuff
  migration: introduce icount field for snapshots
  qcow2: introduce icount field for snapshots
  replay: provide an accessor for rr filename
  replay: don't record interrupt poll
  configure: don't enable ASLR for --enable-debug Windows builds
  configure: consistently pass CFLAGS/CXXFLAGS/LDFLAGS to meson
  configure: do not clobber environment CFLAGS/CXXFLAGS/LDFLAGS
  dtc: Convert Makefile bits to meson bits
  slirp: Convert Makefile bits to meson bits
  accel/tcg: use current_machine as it is always set for softmmu
  ...

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