Merge remote-tracking branch 'remotes/kraxel/tags/ui-20180409-pull-request' into...

sdl2: fix kbd regression (compared to sdl1), cleanups.

# gpg: Signature made Mon 09 Apr 2018 10:40:21 BST
# gpg:                using RSA key 4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/ui-20180409-pull-request:
  sdl2: drop dead code
  sdl2: drop QEMU_KEY_BACKSPACE special case
  sdl2: enable ctrl modifier keys for text consoles
  sdl2: track kbd modifier state unconditionally
  ui: add ctrl modifier support to kbd_put_qcode_console()
  sdl2: Remove unused epoxy include

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