Minor clarifications in the introductory paragraph.

Doc/lib/libexcs.tex

@@ -4,12 +4,13 @@
 \modulesynopsis{Standard exceptions classes.}
 
 
-Exceptions can be class objects or string objects.  While
+Exceptions can be class objects or string objects.  Though most
-traditionally most exceptions have been string objects, in Python
+exceptions have been string objects in past versions of Python, in
-1.5, all standard exceptions have been converted to class objects,
+Python 1.5 and newer versions, all standard exceptions have been
-and users are encouraged to do the same.  The exceptions are defined
+converted to class objects, and users are encouraged to do the same.
-in the module \module{exceptions}; this module never needs to be
+The exceptions are defined in the module \module{exceptions}.  This
-imported explicitly.
+module never needs to be imported explicitly: the exceptions are
+provided in the built-in namespace.
 
 Two distinct string objects with the same value are considered different
 exceptions.  This is done to force programmers to use exception names