bug#3137: 23.0.92; doc of compilation-get-file-structure

Doc string:
 
 Retrieve FILE's file-structure or create a new one.
 FILE should be (FILENAME) or (RELATIVE-FILENAME . DIRNAME).
 In the former case, FILENAME may be relative or absolute.
 
 The file-structure looks like this:
   (list (list FILENAME [DIR-FROM-PREV-MSG]) FMT LINE-STRUCT...)
 
So what are DIR-FROM-PREV-MSG, FMT, and LINESTRUCT?
 
 
 
In GNU Emacs 23.0.92.1 (i386-mingw-nt5.1.2600)
 of 2009-03-30 on SOFT-MJASON
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4)'