Field descriptions are missing when header files are included each other.

[Takao Fujiwara <tfujiwar redhat com>]

I have ibusproperty.h and ibusproplist.h and the header files are included each other.
If the structure has a member, gtkdoc-mkdb outputs a warning:

./a/ibusproplist.h:49: warning: Field description for IBusPropList::properties is missing in source code 
comment block.

I prepared 4 files for the test:

https://fujiwara.fedorapeople.org/ibus/20150709/a.sgml
https://fujiwara.fedorapeople.org/ibus/20150709/ibusproperty.h
https://fujiwara.fedorapeople.org/ibus/20150709/ibusproplist.h
https://fujiwara.fedorapeople.org/ibus/20150709/ibustypes.h

I run the gtk-doc commands:

% ls a
ibusproperty.h  ibusproplist.h  ibustypes.h
% gtkdoc-scan --module=ibus --source-dir=./a --rebuild-sections
% gtkdoc-mktmpl --module=ibus
% gtkdoc-mkdb --module=ibus --output-format=xml --expand-content-files="" --main-sgml-file=a.sgml 
--source-dir=./a --xml-mode --output-format=xml

Then I got the above warning.

How can I fix the problem?