Merge remote-tracking branch 'remotes/pmaydell/tags/pull-target-arm-20150626' into staging

target-arm queue:
 * Change the virt board's default interface type for block devices to virtio
 * Improve some error messages that will now be triggered by some incorrect
   but previously worked-by-accident command lines
 * Print ELR if we're doing debug logging of AArch64 exception entry
 * Handle the "completely empty semihosting commandline" correctly for
   softmmu (we already did for linux-user)
 * Add GICv2m description to ACPI tables for virt board
 * Fix some incorrect table revision entries in virt board ACPI tables

# gpg: Signature made Fri Jun 26 14:29:39 2015 BST using RSA key ID 14360CDE
# gpg: Good signature from "Peter Maydell <peter.maydell@linaro.org>"

* remotes/pmaydell/tags/pull-target-arm-20150626:
  hw/arm/virt: Make block devices default to virtio
  qdev-properties-system: Improve error message for drive assignment conflict
  qdev-properties-system: Change set_pointer's parse callback to use Error
  target-arm: A64: Print ELR when taking exceptions
  target-arm: default empty semihosting cmdline
  hw/arm/virt-acpi-build: Add GICv2m description in ACPI MADT table
  hw/arm/virt-acpi-build: Fix table revision and some comments

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