Document filterwarnings(..., append=<bool>).
diff --git a/Doc/lib/libwarnings.tex b/Doc/lib/libwarnings.tex
index ffb0afb..051c79d 100644
--- a/Doc/lib/libwarnings.tex
+++ b/Doc/lib/libwarnings.tex
@@ -178,8 +178,10 @@
\begin{funcdesc}{filterwarnings}{action\optional{,
message\optional{, category\optional{,
- module\optional{, lineno}}}}}
-Insert an entry into the list of warnings filters (at the front).
+ module\optional{, lineno\optional{, append}}}}}}
+Insert an entry into the list of warnings filters. The entry is
+inserted at the front by default; if \var{append} is true, it is
+inserted at the end.
This checks the types of the arguments, compiles the message and
module regular expressions, and inserts them as a tuple in front
of the warnings filter. Entries inserted later override entries