qapi: add QMP input visitor

A type of Visiter class that is used to walk a qobject's
structure and assign each entry to the corresponding native C type.
Command marshaling function will use this to pull out QMP command
parameters recieved over the wire and pass them as native arguments
to the corresponding C functions.

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@gmail.com>
diff --git a/qerror.h b/qerror.h
index 16c830d..9a9fa5b 100644
--- a/qerror.h
+++ b/qerror.h
@@ -124,6 +124,9 @@
 #define QERR_JSON_PARSE_ERROR \
     "{ 'class': 'JSONParseError', 'data': { 'message': %s } }"
 
+#define QERR_BUFFER_OVERRUN \
+    "{ 'class': 'BufferOverrun', 'data': {} }"
+
 #define QERR_KVM_MISSING_CAP \
     "{ 'class': 'KVMMissingCap', 'data': { 'capability': %s, 'feature': %s } }"