The command name for the suspend action does not need to be
strdup'd. The constant string can be used directly. This
also means the code can be trivially rearranged to make the
switch clearer

* src/util/virnodesuspend.c: Remove strdup of cmdString

To avoid probing the host power management features on any
call to virInitialize, only initialize the mutex in
virNodeSuspendInit. Do lazy load of the supported PM target
mask when it is actually needed

* src/util/virnodesuspend.c: Lazy init of supported features

If we ensure that virNodeSuspendGetTargetMask always resets
*bitmask to zero upon failure, there is no need for the
powerMgmt_valid field.

* src/util/virnodesuspend.c: Ensure *bitmask is zero upon
  failure
* src/conf/capabilities.c, src/conf/capabilities.h: Remove
  powerMgmt_valid field
* src/qemu/qemu_capabilities.c: Remove powerMgmt_valid

The node suspend capabilities APIs should not have been put into
util.[ch]. Instead move them into virnodesuspend.[ch]

* src/util/util.c, src/util/util.h: Remove suspend capabilities APIs
* src/util/virnodesuspend.c, src/util/virnodesuspend.h: Add
  suspend capabilities APIs
* src/qemu/qemu_capabilities.c: Include virnodesuspend.h

Rename virGetPMCapabilities to virNodeSuspendGetTargetMask and
virDiscoverHostPMFeature to virNodeSuspendSupportsTarget.

* src/util/util.c, src/util/util.h: Rename APIs
* src/qemu/qemu_capabilities.c, src/util/virnodesuspend.c: Adjust
  for new names

The VIR_NODE_SUSPEND_TARGET constants are not flags, so they
should just be assigned straightforward incrementing values.

* include/libvirt/libvirt.h.in: Change VIR_NODE_SUSPEND_TARGET
  values
* src/util/virnodesuspend.c: Fix suspend target checks

Add the core functions that implement the functionality of the API.
Suspend is done by using an asynchronous mechanism so that we can return
the status to the caller before the host gets suspended. This asynchronous
operation is achieved by suspending the host in a separate thread of
execution. However, returning the status to the caller is only best-effort,
but not guaranteed.

To resume the host, an RTC alarm is set up (based on how long we want to
suspend) before suspending the host. When this alarm fires, the host
gets woken up.

Suspend-to-RAM operation on a host running Linux can take upto more than 20
seconds, depending on the load of the system. (Freezing of tasks, an operation
preceding any suspend operation, is given up after a 20 second timeout).
And Suspend-to-Disk can take even more time, considering the time required
for compaction, creating the memory image and writing it to disk etc.
So, we do not allow the user to specify a suspend duration of less than 60
seconds, to be on the safer side, since we don't want to prematurely declare
failure when we only had to wait for some more time.