xl / libxl: push parsing of SSID and CPU pool ID down to libxl

xl / libxl: push parsing of SSID and CPU pool ID down to libxl

This patch pushes parsing of "init_seclabel", "seclabel",
"device_model_stubdomain_seclabel" and "pool" down to libxl level.

Originally the parsing is done in xl level, which is not ideal because
libxl won't have the truely relevant information. With this patch libxl
holds important information by itself.

The libxl IDL is extended to hold the string of labels and pool name.
And if there those strings are present they take precedence over the
numeric representations.

As all relevant structures (libxl_dominfo etc) have a field called
X_name / X_label now, a string is also copied there so that callers
won't have to do ID to name / label translation.

In order to be compatible with users of older versions of libxl, this
patch also defines LIBXL_HAVE_SSID_LABEL and LIBXL_HAVE_CPUPOOL_NAME. If
they are defined, the respective strings are available. And if those
strings are not NULL, libxl will do the parsing and ignore the numeric
values.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Cc: Dario Faggioli <dario.faggioli@citrix.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Ian Campbell <ian.campbell@citrix.com>