Fixed index module reference.

Changed references to regex/regsub modules to point to re.
diff --git a/Doc/lib/libstring.tex b/Doc/lib/libstring.tex
index 3d0631a..cc3f34f 100644
--- a/Doc/lib/libstring.tex
+++ b/Doc/lib/libstring.tex
@@ -4,9 +4,9 @@
 \stmodindex{string}
 
 This module defines some constants useful for checking character
-classes and some useful string functions.  See the modules
-\code{regex} and \code{regsub} for string functions based on regular
-expressions.
+classes and some useful string functions.  See the module
+\code{re} for string functions based on regular expressions.
+\refstmodindex{re}
 
 The constants defined in this module are are:
 
@@ -244,4 +244,4 @@
 replaces parts of itself with the implementation from \code{strop}.
 After initialization, there is \emph{no} overhead in using
 \code{string} instead of \code{strop}.
-\bimodindex{strop}
+\refbimodindex{strop}