Update version and changelog to sync with stable branch

Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

Changelog

+version 0.12.0:
+
+  - Update to SeaBIOS 0.5.0
+  - e1000: fix device link status in Linux (Anthony Liguori)
+  - monitor: fix QMP for balloon command (Luiz Capitulino)
+  - QMP: Return an empty dict by default (Luiz Capitulino)
+  - QMP: Only handle converted commands (Luiz Capitulino)
+  - pci: support PCI based option rom loading (Gerd Hoffman/Anthony Liguori)
+  - Fix backcompat for hotplug of SCSI controllers (Daniel P. Berrange)
+  - fdc: fix migration from 0.11 (Juan Quintela)
+  - vmware-vga: fix segv on cursor resize. (Dave Airlie)
+  - vmware-vga: various fixes (Dave Airlie/Anthony Liguori)
+  - qdev: improve property error reporting. (Gerd Hoffmann)
+  - fix vga names in default_list (Gerd Hoffmann)
+  - usb-host: check mon before using it. (Gerd Hoffmann)
+  - usb-net: use qdev for -usbdevice (Gerd Hoffmann)
+  - monitor: Catch printing to non-existent monitor (Luiz Capitulino)
+  - Avoid permanently disabled QEMU monitor when UNIX migration fails (Daniel P. Berrange)
+  - Fix loading of ELF multiboot kernels (Kevin Wolf)
+  - qemu-io: Fix memory leak (Kevin Wolf)
+  - Fix thinko in linuxboot.S (Paolo Bonzini)
+  - target-i386: Fix evaluation of DR7 register (Jan Kiszka)
+  - vnc: hextile: do not generate ForegroundSpecified and SubrectsColoured tiles (Anthony Liguori)
+  - S390: Bail out without KVM (Alexander Graf)
+  - S390: Don't tell guest we're updating config space (Alexander Graf)
+  - target-s390: Fail on unknown instructions (Alexander Graf)
+  - osdep: Fix runtime failure on older Linux kernels (Andre Przywara)
+  - Fix a make -j race (Juergen Lock)
+  - target-alpha: Fix generic ctz64. (Richard Henderson)
+  - s390: Fix buggy assignment (Stefan Weil)
+  - target-mips: fix user-mode emulation startup (Nathan Froyd)
+  - target-i386: Update CPUID feature set for TCG (Andre Przywara)
+  - s390: fix build on 32 bit host (Michael S. Tsirkin)
+	
+version 0.12.0-rc2:
+
+  - v2: properly save kvm system time msr registers (Glauber Costa)
+  - convert more monitor commands to qmp (Luiz Capitulino)
+  - vnc: fix capslock tracking logic. (Gerd Hoffmann)
+  - QemuOpts: allow larger option values. (Gerd Hoffmann)
+  - scsi: fix drive hotplug. (Gerd Hoffmann)
+  - pci: don't hw_error() when no slot is available. (Gerd Hoffmann)
+  - pci: don't abort() when trying to hotplug with acpi off. (Gerd Hoffmann)
+  - allow default devices to be implemented in config file (Gerd Hoffman)
+  - vc: colorize chardev title line with blue background. (Gerd Hoffmann)
+  - chardev: make chardevs specified in config file work. (Gerd Hoffmann)
+  - qdev: also match bus name for global properties (Gerd Hoffmann)
+  - qdev: add command line option to set global defaults for properties. (Gerd Hoffmann)
+  - kvm: x86: Save/restore exception_index (Jan Kiszka)
+  - qdev: Replace device names containing whitespace (Markus Armbruster)
+  - fix rtc-td-hack on host without high-res timers (Gleb Natapov)
+  - virtio: verify features on load (Michael S. Tsirkin)
+  - vmware_vga: add rom file so that it boots. (Dave Airlie)
+  - Do not abort on qemu_malloc(0) in production builds (Anthony Liguori)
+  - Fix ARM userspace strex implementation. (Paul Brook)
+  - qemu: delete rule target on error (Michael S. Tsirkin)
+  - QMP: add human-readable description to error response (Markus Armbruster)
+  - convert more monitor commands to QError (Markus Armbruster)
+  - monitor: Fix double-prompt after "change vnc passwd BLA" (Markus Armbruster)
+  - monitor: do_cont(): Don't ask for passwords (Luiz Capitulino)
+  - monitor: Introduce 'block_passwd' command (Luiz Capitulino)
+  - pci: interrupt disable bit support (Michael S. Tsirkin)
+  - pci: interrupt status bit implementation (Michael S. Tsirkin)
+  - pci: prepare irq code for interrupt state (Michael S. Tsirkin)
+  - msix: function mask support (Michael S. Tsirkin)
+  - msix: macro rename for function mask support (Michael S. Tsirkin)
+  - cpuid: Fix multicore setup on Intel (Andre Przywara)
+  - kvm: x86: Fix initial kvm_has_msr_star (Jan Kiszka)
+  - Update OpenBIOS images to r640 (Aurelien Jarno)	
+
 version 0.10.2:
 
   - fix savevm/loadvm (Anthony Liguori)

VERSION

-0.11.50
+0.12.50