#1196: document default radix for int().

Doc/lib/libfuncs.tex

@@ -533,7 +533,7 @@ class C:
   string, it must contain a possibly signed decimal number
   representable as a Python integer, possibly embedded in whitespace.
   The \var{radix} parameter gives the base for the
-  conversion and may be any integer in the range [2, 36], or zero.  If
+  conversion (which is 10 by default) and may be any integer in the range [2, 36], or zero.  If
   \var{radix} is zero, the proper radix is guessed based on the
   contents of string; the interpretation is the same as for integer
   literals.  If \var{radix} is specified and \var{x} is not a string,