Merge branch 'staging' of git://xenbits.xen.org/people/konradwilk/xen into staging

* 'staging' of git://xenbits.xen.org/people/konradwilk/xen:
  Introduce the pvcalls header
  Introduce the Xen 9pfs transport header
  xen: introduce a C99 headers check
  ring.h: introduce macros to handle monodirectional rings with multiple req sizes
  tmem: Parse UUIDs correctly.
  tmem: Fix tmem-shared-auth 'auth' values
  tmem: By default to join an shared pool it must be authorized.
  xen/libxc: Move TMEM_AUTH to XEN_SYSCTL_TMEM_OP_SET_AUTH
  xen/libcx/tmem: Replace TMEM_RESTORE_NEW with XEN_SYSCTL_TMEM_OP_SET_POOLS
  displif: add ABI for para-virtual display