Don't rely on summary.url anymore, because its value is different
between an esx:// and vpx:// connection. Use host.mountInfo.path
instead.

Don't fallback to lookup by UUID (actually lookup by absolute path)
in esxVI_LookupDatastoreByName when lookup by name fails. Add a
seperate function for this: esxVI_LookupDatastoreByAbsolutePath

Now a vpx:// connection has an explicitly specified host. This
allows to enabled several functions for a vpx:// connection
again, like host UUID, hostname, general node info, max vCPU
count, free memory, migration and defining new domains.

Lookup datacenter, compute resource, resource pool and host
system once and cache them. This simplifies the rest of the
code and reduces overall HTTP(S) traffic a bit.

esx:// and vpx:// can be mixed freely for a migration.

Ensure that migration source and destination refer to the
same vCenter. Also directly encode the resource pool and
host system object IDs into the migration URI in the prepare
function. Then directly build managed object references in
the perform function instead of re-looking up already known
information.

Add a pointer to the primary context of a connection and use it in all
driver functions that don't dependent on the context type. This includes
almost all functions that deal with a virDomianPtr. Therefore, using
a vpx:// connection allows you to perform all the usual domain related
actions like start, destroy, suspend, resume, dumpxml etc.

Some functions that require an explicitly specified ESX server don't work
yet. This includes the host UUID, the hostname, the general node info, the
max vCPU count and the free memory. Also not working yet are migration and
defining new domains.

Eliminate almost all backward jumps by replacing this common pattern:

int
some_random_function(void)
{
    int result = 0;
    ...

  cleanup:
    <unconditional cleanup code>
    return result;

  failure:
    <cleanup code in case of an error>
    result = -1;
    goto cleanup
}

with this simpler pattern:

int
some_random_function(void)
{
    int result = -1;
    ...
    result = 0;

  cleanup:
    if (result < 0) {
        <cleanup code in case of an error>
    }

    <unconditional cleanup code>
    return result;
}

Add a bool success variable in functions that don't have a int result
that can be used for the new pattern.

Also remove some unnecessary memsets in error paths.

Allows listing existing pools and requesting information about them.

Alter the esxVI_ProductVersion enum in a way that allows to check for
product type by masking.

Also define ESX_ERROR and ESX_VI_ERROR in a central place, instead of
defining them in each source file.

Add ESX_ERROR and ESX_VI_ERROR to the msg_gen_function list in cfg.mk.

Update po/POTFILES.in accordingly.

Replace 'method' with 'function' and get the filename's suffix right.

Also add vol wiping to ESX storage driver struct

Prior to this patch, there was an inconsistent mix between GNU and C99.

For consistency, and potential portability to other compilers, stick
with the C99 vararg macro syntax.

* src/conf/cpu_conf.c (virCPUReportError): Use C99 rather than GNU
  vararg macro syntax.
* src/conf/domain_conf.c (virDomainReportError): Likewise.
* src/conf/domain_event.c (eventReportError): Likewise.
* src/conf/interface_conf.c (virInterfaceReportError): Likewise.
* src/conf/network_conf.c (virNetworkReportError): Likewise.
* src/conf/node_device_conf.h (virNodeDeviceReportError): Likewise.
* src/conf/secret_conf.h (virSecretReportError): Likewise.
* src/conf/storage_conf.h (virStorageReportError): Likewise.
* src/esx/esx_device_monitor.c (ESX_ERROR): Use C99 rather than
  GNU vararg macro syntax.
* src/esx/esx_driver.c (ESX_ERROR): Likewise.
* src/esx/esx_interface_driver.c (ESX_ERROR): Likewise.
* src/esx/esx_network_driver.c (ESX_ERROR): Likewise.
* src/esx/esx_secret_driver.c (ESX_ERROR): Likewise.
* src/esx/esx_storage_driver.c (ESX_ERROR): Likewise.
* src/esx/esx_util.c (ESX_ERROR): Likewise.
* src/esx/esx_vi.c (ESX_VI_ERROR): Likewise.
* src/esx/esx_vi_methods.c (ESX_VI_ERROR): Likewise.
* src/esx/esx_vi_types.c (ESX_VI_ERROR): Likewise.
* src/esx/esx_vmx.c (ESX_ERROR): Likewise.
* src/util/hostusb.c (usbReportError): Use C99 rather than GNU
  vararg macro syntax.
* src/util/json.c (virJSONError): Likewise.
* src/util/macvtap.c (ReportError): Likewise.
* src/util/pci.c (pciReportError): Likewise.
* src/util/stats_linux.c (virStatsError): Likewise.
* src/util/util.c (virUtilError): Likewise.
* src/util/xml.c (virXMLError): Likewise.
* src/xen/proxy_internal.c (virProxyError): Use C99 rather than
  GNU vararg macro syntax.
* src/xen/sexpr.c (virSexprError): Likewise.
* src/xen/xen_driver.c (xenUnifiedError): Likewise.
* src/xen/xen_hypervisor.c (virXenError): Likewise.
* src/xen/xen_inotify.c (virXenInotifyError): Likewise.
* src/xen/xend_internal.c (virXendError): Likewise.
* src/xen/xm_internal.c (xenXMError): Likewise.
* src/xen/xs_internal.c (virXenStoreError): Likewise.
* src/cpu/cpu.h (virCPUReportError): Use C99 rather than GNU
  vararg macro syntax.
* src/datatypes.c (virLibConnError): Likewise.
* src/interface/netcf_driver.c (interfaceReportError): Likewise.
* src/libvirt.c (virLibStreamError): Likewise.
* src/lxc/lxc_conf.h (lxcError): Likewise.
* src/network/bridge_driver.c (networkReportError): Likewise.
* src/nodeinfo.c (nodeReportError): Likewise.
* src/opennebula/one_conf.h (oneError): Likewise.
* src/openvz/openvz_conf.h (openvzError): Likewise.
* src/phyp/phyp_driver.c (PHYP_ERROR): Likewise.
* src/qemu/qemu_conf.h (qemuReportError): Likewise.
* src/remote/remote_driver.c (errorf): Likewise.
* src/security/security_driver.h (virSecurityReportError): Likewise.
* src/test/test_driver.c (testError): Likewise.
* src/uml/uml_conf.h (umlReportError): Likewise.
* src/vbox/vbox_driver.c (vboxError): Likewise.
* src/vbox/vbox_tmpl.c (vboxError): Likewise.

This stops libvirt from probing for a libvirtd on the ESX server and
sets the base for the implementation of the secondary drivers.