* src/qemu/qemu_capabilities.h (QEMUD_CMD_FLAG_MIGRATE_QEMU_FD):
New enum value.
* src/qemu/qemu_capabilities.c (qemuCapsComputeCmdFlags): Populate
flags according to qemu version.
* tests/qemuhelptest.c (mymain): Adjust test.

The qemu_conf.c code is doing three jobs, driver config file
loading, QEMU capabilities management and QEMU command line
management. Move the capabilities code into its own file

* src/qemu/qemu_capabilities.c, src/qemu/qemu_capabilities.h: New
  capabilities management code
* src/qemu/qemu_conf.c, src/qemu/qemu_conf.h: Delete capabilities
  code
* src/qemu/qemu_conf.h: Adapt for API renames
* src/Makefile.am: add src/qemu/qemu_capabilities.c