Use the new module-key for the FL module when hyperlinking (the old

one caused problems on case-insensitive file systems).

Doc/lib/libfl.tex

@@ -14,7 +14,8 @@ with version 2.0b.
 
 Most functions are literal translations of their C equivalents,
 dropping the initial \samp{fl_} from their name.  Constants used by
-the library are defined in module \refmodule{FL} described below.
+the library are defined in module \refmodule[fl-constants]{FL}
+described below.
 
 The creation of objects is a little different in Python than in C:
 instead of the `current form' maintained by the library to which new