Move __builtins__.trunc() to math.trunc() per
http://mail.python.org/pipermail/python-dev/2008-January/076626.html and issue
1965.
diff --git a/Doc/library/math.rst b/Doc/library/math.rst
index b111dd1..47ebadb 100644
--- a/Doc/library/math.rst
+++ b/Doc/library/math.rst
@@ -103,6 +103,14 @@
    Return the fractional and integer parts of *x*.  Both results carry the sign of
    *x*, and both are floats.
 
+
+.. function:: trunc(x)
+
+   Return the :class:`Real` value *x* truncated to an :class:`Integral` (usually
+   a long integer). Delegates to ``x.__trunc__()``.
+
+   .. versionadded:: 2.6
+
 Note that :func:`frexp` and :func:`modf` have a different call/return pattern
 than their C equivalents: they take a single argument and return a pair of
 values, rather than returning their second return value through an 'output