Remove the <stdbool.h> header from all source files / headers
and just put it into internal.h

* src/internal.h: Add <stdbool.h>

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.

We try to use that command first when setting a VNC/SPICE password. If
that doesn't work we fallback to the legacy VNC only password

Allow an expiry time to be set, if that doesn't work, throw an error
if they try to use SPICE.

Change since v1:
- moved qemuInitGraphicsPasswords to qemu_hotplug, renamed
  to qemuDomainChangeGraphicsPasswords.
- updated what looks like a typo (that appears to work anyway) in
  initial patch from Daniel:
    - ret = qemuInitGraphicsPasswords(driver, vm,
    -                                 VIR_DOMAIN_GRAPHICS_TYPE_SPICE,
    -                                 &vm->def->graphics[0]->data.vnc.auth,
    -                                 driver->vncPassword);
    + ret = qemuInitGraphicsPasswords(driver, vm,
    +                                 VIR_DOMAIN_GRAPHICS_TYPE_SPICE,
    +                                 &vm->def->graphics[0]->data.spice.auth,
    +                                 driver->spicePassword);

Based on patch by Daniel P. Berrange <berrange@redhat.com>.

The QEMU driver file is far too large. Move all the hotplug
helper code out into a separate file. No functional change.

* src/qemu/qemu_hotplug.c, src/qemu/qemu_hotplug.h,
  src/Makefile.am: Add hotplug helper file
* src/qemu/qemu_driver.c: Delete hotplug code