This is done for two reasons:
- we are getting very close to 64 flags which is the maximum we can use
  with unsigned long long
- by using LL constants in enum we already violates C99 constraint that
  enum values have to fit into int

The new name complies more with the fact that it contains a set of
qemuCapsFlags.

Three new functions (qemuCapsSet, qemuCapsClear, and qemuCapsGet) were
introduced replacing direct bit operations.

The new names comply more with the fact that they are all members of
enum qemuCapsFlags.

The introduction of the v3 migration protocol, along with
support for migration cookies, will significantly expand
the size of the migration code. Move it all to a separate
file to make it more manageable

The functions are not moved 100%. The API entry points
remain in the main QEMU driver, but once the public
virDomainPtr is resolved to the internal virDomainObjPtr,
all following code is moved.

This will allow the new v3 API entry points to call into the
same shared internal migration functions

* src/qemu/qemu_domain.c, src/qemu/qemu_domain.h: Add
  qemuDomainFormatXML helper method
* src/qemu/qemu_driver.c: Remove all migration code
* src/qemu/qemu_migration.c, src/qemu/qemu_migration.h: Add
  all migration code.