Added index entry and \label{} for exceptions module. This isn't in the

normal modules portion of the manual, but that's the basic effect of this
section with the 1.5 change in exception support.

Doc/lib/libexcs.tex

@@ -1,4 +1,6 @@
 \section{Built-in Exceptions}
+\label{module-exceptions}
+\stmodindex{exceptions}
 
 Exceptions can be class objects or string objects.  While
 traditionally, most exceptions have been string objects, in Python

Doc/libexcs.tex

@@ -1,4 +1,6 @@
 \section{Built-in Exceptions}
+\label{module-exceptions}
+\stmodindex{exceptions}
 
 Exceptions can be class objects or string objects.  While
 traditionally, most exceptions have been string objects, in Python