qapi: Drop unused and useless parameters and variables

gen_sync_call()'s parameter indent is useless: gen_sync_call() uses it
only as optional argument for push_indent() and pop_indent(), their
default is four, and gen_sync_call()'s only caller passes four.  Drop
the parameter.

gen_visitor_input_containers_decl()'s parameter obj is always
"QOBJECT(args)".  Use that, and drop the parameter.

Drop unused parameters of gen_marshal_output(),
gen_marshal_input_decl(), generate_visit_struct_body(),
generate_visit_list(), generate_visit_enum(), generate_declaration(),
generate_enum_declaration(), generate_decl_enum().

Drop unused variables in generate_event_enum_lookup(),
generate_enum_lookup(), generate_visit_struct_fields(), check_event().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

scripts/qapi-types.py

@@ -108,7 +108,6 @@ def generate_enum_lookup(name, values):
 const char * const %(name)s_lookup[] = {
 ''',
                 name=c_name(name))
-    i = 0
     for value in values:
         index = c_enum_const(name, value)
         ret += mcgen('''