qapi: Fix generation of 'size' builtin type

We were missing the 'size' builtin type (which means that QAPI using
[ 'size' ] would fail to compile).

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
diff --git a/scripts/qapi.py b/scripts/qapi.py
index 2b5775d..d470347 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -29,6 +29,7 @@
     'uint16':   'QTYPE_QINT',
     'uint32':   'QTYPE_QINT',
     'uint64':   'QTYPE_QINT',
+    'size':     'QTYPE_QINT',
 }
 
 def error_path(parent):