Add decrepit, initially containing CAST and Blowfish.

decrepit will contain algorithms that we really wish didn't exist any
longer. It won't be built by default in Chromium etc, but the code
will exist for crummy code that still needs it.

Change-Id: Ic307f5f0a69efe9e0a5fd54052f49d219e90dcdd
diff --git a/CMakeLists.txt b/CMakeLists.txt
index dd7183e..6c95b7e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -117,3 +117,4 @@
 add_subdirectory(ssl)
 add_subdirectory(ssl/test)
 add_subdirectory(tool)
+add_subdirectory(decrepit)