docs/libxl: Re-specify XENSTORE_DATA as EMULATOR_XENSTORE_DATA

The legacy "toolstack" record as implemented in libxl turns out not to
be 32/64bit safe.  As migration v2 has not shipped yet, take this
opportunity to adjust the specification and fix the incompatibility.

Libxl shall loose all knowledge of the old "toolstack" blob and use this
EMULATOR_XENSTORE_DATA record instead.  Compatibility shall be handled
by the legacy conversion script.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

tools/python/scripts/convert-legacy-stream

@@ -174,7 +174,7 @@ def write_libxl_xenstore_data(data):
 
 def write_libxl_emulator_context(blob):
     write_record(libxl.REC_TYPE_emulator_context,
-                 pack(libxl.EMULATOR_CONTEXT_FORMAT,
+                 pack(libxl.EMULATOR_HEADER_FORMAT,
                       libxl.EMULATOR_ID_unknown, 0) + blob)
 
 def rdexact(nr_bytes):