extension: Handle pages with listed symbols but no generated symbols
extension: Handle pages with listed symbols but no generated symbols

If a .c file has a section which lists symbols to import but doesn't
define any symbol itself, the imported symbols where skipped, make
sure we handle that case properly.

thiblahute/hotdoc,hotdoc/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc,hotdoc/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc,thiblahute/hotdoc,hotdoc/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc,thiblahute/hotdoc