qapi: Implement boxed event argument documentation

Generate a reference "Arguments: the members of ...", just like we do
for commands since commit c2dd311cb7 "qapi2texi: Implement boxed
argument documentation".

No change to generated QMP documentation; we don't yet use boxed
events outside tests/.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20191024110237.30963-7-armbru@redhat.com>
diff --git a/tests/qapi-schema/doc-good.json b/tests/qapi-schema/doc-good.json
index df50a87..d992e71 100644
--- a/tests/qapi-schema/doc-good.json
+++ b/tests/qapi-schema/doc-good.json
@@ -160,7 +160,6 @@
 
 ##
 # @EVT-BOXED:
-# BUG: generated doc misses arguments
 ##
 { 'event': 'EVT-BOXED',  'boxed': true,
   'data': 'Object' }
diff --git a/tests/qapi-schema/doc-good.out b/tests/qapi-schema/doc-good.out
index 8cc29fc..4c9406a 100644
--- a/tests/qapi-schema/doc-good.out
+++ b/tests/qapi-schema/doc-good.out
@@ -196,4 +196,4 @@
 <- out
 doc symbol=EVT-BOXED
     body=
-BUG: generated doc misses arguments
+
diff --git a/tests/qapi-schema/doc-good.texi b/tests/qapi-schema/doc-good.texi
index 98aa78e1..d4b15da 100644
--- a/tests/qapi-schema/doc-good.texi
+++ b/tests/qapi-schema/doc-good.texi
@@ -279,7 +279,9 @@
 
 @deftypefn Event {} EVT-BOXED
 
-BUG: generated doc misses arguments
+
+
+@b{Arguments:} the members of @code{Object}
 
 @end deftypefn