this patch improve the functions:
-find_all_headers -> make _allheaders a dict: _allheaders['<modulename>'] contains the list of all headers for that module
-headers_of(modulename) -> it return the list of headers for that module, or a empty list for module that not have headers

Change-Id: I7e4e2bf063ccf6fd2e3e5155b58d2be2412480ba
Reviewed-on: https://gerrit.libreoffice.org/33255Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: jan iversen <jani@documentfoundation.org>