Fix for bug https://bugzilla.redhat.com/show_bug.cgi?id=618970

The "prepare" hook is called very early in the VM statup process
before device labeling, so that it can allocate ressources not
managed by libvirt, such as DRBD, or for instance create missing
bridges and vlan interfaces.
* src/util/hooks.c src/util/hooks.h: add definitions for new hooks
  VIR_HOOK_QEMU_OP_PREPARE and VIR_HOOK_QEMU_OP_RELEASE
* src/qemu/qemu_process.c: use them in qemuProcessStart and
  qemuProcessStop()

This proof of concept shows how two existing uses of virExec
and virRun can be ported to the new virCommand APIs, and how
much simpler the code becomes

* bootstrap.conf (gnulib_modules): Add configmake.
* daemon/Makefile.am (libvirtd_CFLAGS): Drop defines provided by
gnulib.
* src/Makefile.am (INCLUDES): Likewise.
* tests/Makefile.am (INCLUDES): Likewise.
* tools/Makefile.am (virsh_CFLAGS): Likewise.
* daemon/libvirtd.c (qemudInitPaths, usage, main): Update
clients.
* src/cpu/cpu_map.c (CPUMAPFILE): Likewise.
* src/driver.c (DEFAULT_DRIVER_DIR): Likewise.
* src/internal.h (_): Likewise.
* src/libvirt.c (virInitialize): Likewise.
* src/lxc/lxc_conf.h (LXC_CONFIG_DIR, LXC_STATE_DIR, LXC_LOG_DIR):
Likewise.
* src/lxc/lxc_conf.c (lxcCapsInit, lxcLoadDriverConfig):
Likewise.
* src/network/bridge_driver.c (NETWORK_PID_DIR)
(NETWORK_STATE_DIR, DNSMASQ_STATE_DIR, networkStartup): Likewise.
* src/nwfilter/nwfilter_driver.c (nwfilterDriverStartup):
Likewise.
* src/qemu/qemu_conf.c (qemudLoadDriverConfig): Likewise.
* src/qemu/qemu_driver.c (qemudStartup): Likewise.
* src/remote/remote_driver.h (LIBVIRTD_PRIV_UNIX_SOCKET)
(LIBVIRTD_PRIV_UNIX_SOCKET_RO, LIBVIRTD_CONFIGURATION_FILE)
(LIBVIRT_PKI_DIR): Likewise.
* src/secret/secret_driver.c (secretDriverStartup): Likewise.
* src/security/security_apparmor.c (VIRT_AA_HELPER): Likewise.
* src/security/virt-aa-helper.c (main): Likewise.
* src/storage/storage_backend_disk.c (PARTHELPER): Likewise.
* src/storage/storage_driver.c (storageDriverStartup): Likewise.
* src/uml/uml_driver.c (TEMPDIR, umlStartup): Likewise.
* src/util/hooks.c (LIBVIRT_HOOK_DIR): Likewise.
* tools/virsh.c (main): Likewise.
* docs/hooks.html.in: Likewise.

Using automated replacement with sed and editing I have now replaced all
occurrences of close() with VIR_(FORCE_)CLOSE() except for one, of
course. Some replacements were straight forward, others I needed to pay
attention. I hope I payed attention in all the right places... Please
have a look. This should have at least solved one more double-close
error.

* src/util/hooks.c (virHookLxcOp): Use correct bound.

* configure.ac: Drop sys/wait.h check.
* src/libvirt.c (includes): Use header unconditionally.
* src/remote/remote_driver.c (includes): Likewise.
* src/storage/storage_backend.c (includes): Likewise.
* src/util/ebtables.c (includes): Likewise.
* src/util/hooks.c (includes): Likewise.
* src/util/iptables.c (includes): Likewise.
* src/util/util.c (includes): Likewise.

* src/conf/nwfilter_conf.c src/util/hooks.c: added spaces to avoid
  "make syntax-check" failures

The network filter / snapshot / hooks code introduced some
non-portable pices that broke the win32 build

* configure.ac: Check for net/ethernet.h required by nwfile config
   parsing code
* src/conf/nwfilter_conf.c: Define ethernet protocol  constants
  if net/ethernet.h is missing
* src/util/hooks.c: Disable hooks build on Win32 since it lacks
  fork/exec/pipe
* src/util/threads-win32.c: Fix unchecked return value
* tools/virsh.c: Disable SIGPIPE on Win32 since it doesn't exist.
  Fix non-portable strftime() formats

This exports 3 basic routines:
  - virHookInitialize() initializing the hook support by looking for
    scripts availability
  - virHookPresent() used to test if there is a hook for a given driver
  - virHookCall() which actually calls a synchronous script hook with
    the needed parameters
Note that this doesn't expose any public API except for the locations
and arguments passed to the scripts

* src/Makefile.am: add the 2 new files
* src/util/hooks.h src/util/hooks.c: implements the 3 functions
* src/libvirt_private.syms: export the 3 symbols internally
* po/POTFILES.in: add src/util/hooks.c to translatables modules