SF #1442767, docs for os.statvfs miss f_bsize parameter. Will backport.

Doc/lib/libos.tex

@@ -1097,6 +1097,7 @@ Perform a \cfunction{statvfs()} system call on the given path.  The
 return value is an object whose attributes describe the filesystem on
 the given path, and correspond to the members of the
 \ctype{statvfs} structure, namely:
+\member{f_bsize},
 \member{f_frsize},
 \member{f_blocks},
 \member{f_bfree},