dpkg-buildflags(1): -D_FORTIFY_SOURCE=2 goes in CPPFLAGS

In 1.16.1.1~8 (2011-10-02), dpkg-buildflags learned to set
-D_FORTIFY_SOURCE=2 in CPPFLAGS instead of CFLAGS and CXXFLAGS but the
documentation wasn't updated to match.

Reported-by: James Vega <jamessan@debian.org>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Closes: #646073

debian/changelog

@@ -1,7 +1,13 @@
 dpkg (1.16.1.2) UNRELEASED; urgency=low
 
+  [ Raphaël Hertzog ]
   * Fix another typo to correctly set DEB_*_ARCH_BITS in architecture.mk.
 
+  [ Jonathan Nieder ]
+  * Update dpkg-buildflags(1) to note that the processor option
+    -D_FORTIFY_SOURCE=2 is set in CPPFLAGS now instead of CFLAGS and
+    CXXFLAGS. Closes: #646073
+
  -- Raphaël Hertzog <hertzog@debian.org>  Sat, 15 Oct 2011 10:49:21 +0200
 
 dpkg (1.16.1.1) unstable; urgency=low

man/dpkg-buildflags.1

@@ -200,7 +200,7 @@ input and contains "%n".
 .B fortify
 This setting (enabled by default) adds
 .B \-D_FORTIFY_SOURCE=2
-to \fBCFLAGS\fP and \fBCXXFLAGS\fP. During code generation the compiler
+to \fBCPPFLAGS\fP. During code generation the compiler
 knows a great deal of information about buffer sizes (where possible), and
 attempts to replace insecure unlimited length buffer function calls with
 length-limited ones. This is especially useful for old, crufty code.