Cleaned up handling of 64-bit file sizes.

diff --git a/server/file.h b/server/file.h
index fc65810..32a5176 100644
--- a/server/file.h
+++ b/server/file.h
@@ -96,7 +96,7 @@
                                   unsigned int access );
 extern int get_file_unix_fd( struct file *file );
 extern int is_same_file( struct file *file1, struct file *file2 );
-extern int grow_file( struct file *file, int size_high, int size_low );
+extern int grow_file( struct file *file, file_pos_t size );
 extern struct file *create_temp_file( int access );
 extern void file_set_error(void);