i18n: make hggettext use original docstring to compute offset Before this patch, hggettext uses __doc__ of each functions to compute offset of document text. But __doc__ of many functions is already modified by decorators in registrar (e.g. @templatekeyword adds ":NAME: " prefix to it), and hggettext can not find it out in original source. This causes many "unknown offset in ..." warning at "make update-pot", and leaving them might cause overlooking serious problems. This patch makes hggettext use original docstring, which decorators in registrar save into _origdoc, to compute offset. Even after this patch, there are still a few "unknown offset in ..." warning at "make update-pot" for specific reasons. These will be fixed later one by one.