qom: add new dynamic property infrastructure based on Visitors (v2)

qdev properties are settable only during construction and static to classes.
This isn't flexible enough for QOM.

This patch introduces a property interface for qdev that provides dynamic
properties that are tied to objects, instead of classes.  These properties are
Visitor based instead of string based too.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

qerror.c

@@ -185,6 +185,10 @@ static const QErrorStringTable qerror_table[] = {
         .error_fmt = QERR_OPEN_FILE_FAILED,
         .desc      = "Could not open '%(filename)'",
     },
+    {
+        .error_fmt = QERR_PERMISSION_DENIED,
+        .desc      = "Insufficient permission to perform this operation",
+    },
     {
         .error_fmt = QERR_PROPERTY_NOT_FOUND,
         .desc      = "Property '%(device).%(property)' not found",