Ignore deprecation warnings on OS X

Starting with Lion, Apple decided to deprecate the system openssl. We
can start requiring users to install their own openssl once OS X doesn't
ship with it anymore.

changes/bug3643

+  o Minor bugfixes:
+    - Selectively disable deprecation warnings on OS X because Lion started
+      deprecating the shipped copy of openssl. Fixes bug 3643.
+

configure.in

@@ -906,6 +906,15 @@ else
   enable_gcc_warnings_advisory=no
 fi
 
+# OS X Lion started deprecating the system openssl. Let's just disable
+# all deprecation warnings on OS X.
+case "$host_os" in
+
+ darwin*)
+    CFLAGS="$CFLAGS -Wno-deprecated-declarations"
+    ;;
+esac
+
 # Add some more warnings which we use in development but not in the
 # released versions.  (Some relevant gcc versions can't handle these.)
 if test x$enable_gcc_warnings = xyes || test x$enable_gcc_warnings_advisory = xyes; then