Merge remote-tracking branch 'remotes/kraxel/tags/fixes-20200407-pull-request' into staging

fixes for 5.0:
- audio: windows (dsound) fixes.
- vga: ati blitter sanity check fixes.

# gpg: Signature made Tue 07 Apr 2020 10:21:44 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/fixes-20200407-pull-request:
  ati-vga: Fix checks in ati_2d_blt() to avoid crash
  dsoundaudio: dsound_get_buffer_in should honor *size
  dsoundaudio: fix "Could not lock capture buffer" warning
  dsoundaudio: fix never-ending playback loop

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