Make it obvious to 'dumpxml' readers what unit we are using,
since our default of KiB for memory (1024) differs from qemu's
default of MiB; and differs from our use of bytes for storage.

Tests were updated via:

$ find tests/*data tests/*out -name '*.xml' | \
  xargs sed -i 's/<\(memory\|currentMemory\|hard_limit\|soft_limit\|min_guarantee\|swap_hard_limit\)>/<\1 unit='"'KiB'>/"
$ find tests/*data tests/*out -name '*.xml' | \
  xargs sed -i 's/<\(capacity\|allocation\|available\)>/<\1 unit='"'bytes'>/"

followed by a few fixes for the stragglers.

Note that with this patch, the RNG for <memory> still forbids
validation of anything except unit='KiB', since the code silently
ignores the attribute; a later patch will expand <memory> to allow
scaled input in the code and update the RNG to match.

* docs/schemas/basictypes.rng (unit): Add 'bytes'.
(scaledInteger): New define.
* docs/schemas/storagevol.rng (sizing): Use it.
* docs/schemas/storagepool.rng (sizing): Likewise.
* docs/schemas/domaincommon.rng (memoryKBElement): New define; use
for memory elements.
* src/conf/storage_conf.c (virStoragePoolDefFormat)
(virStorageVolDefFormat): Likewise.
* src/conf/domain_conf.h (_virDomainDef): Document unit used
internally.
* src/conf/storage_conf.h (_virStoragePoolDef, _virStorageVolDef):
Likewise.
* tests/*data/*.xml: Update all tests.
* tests/*out/*.xml: Likewise.
* tests/define-dev-segfault: Likewise.
* tests/openvzutilstest.c (testReadNetworkConf): Likewise.
* tests/qemuargv2xmltest.c (blankProblemElements): Likewise.

Assuming a hypervisor that supports multiple smartcard devices in the
guest, this would be a valid XML description:

<devices>
  <smartcard mode='host'/>
  <smartcard mode='host-certificates'>
    <certificate>/path/to/cert1</certificate>
    <certificate>/path/to/cert2</certificate>
    <certificate>/path/to/cert3</certificate>
  </smartcard>
  <smartcard mode='passthrough' type='tcp'>
    <source mode='bind' host='127.0.0.1' service='2001'/>
    <protocol type='raw'/>
  </smartcard>
</devices>

(As of this commit, the qemu hypervisor will be the first
implementation, but it only supports one smartcard.)

* docs/formatdomain.html.in (Smartcard devices): New section.
* docs/schemas/domain.rng (smartcard): New define, used in
devices.
* tests/qemuxml2argvdata/qemuxml2argv-smartcard-host.xml: New file
to test schema.
* tests/qemuxml2argvdata/qemuxml2argv-smartcard-host-certificates.xml:
Likewise.
* tests/qemuxml2argvdata/qemuxml2argv-smartcard-passthrough-tcp.xml:
Likewise.
* tests/qemuxml2argvdata/qemuxml2argv-smartcard-controller.xml:
Likewise.