[toplevel] add support for `ppx_compare` to the infer repl

Summary:
Useful for testing stuff with ppx. Opening `IStd` is needed to open `Core`,
which pulls stuff like `compare_option` into the global namespace, and is
generally useful anyway as it's the excpected development environment for
infer.

Reviewed By: mbouaziz

Differential Revision: D6834071

fbshipit-source-id: 26a1304

scripts/toplevel_init

@@ -3,16 +3,24 @@
 (* load dependencies *)
 #use "topfind";;
 #thread;;
+#require "ANSITerminal";;
+#require "atdgen";;
 #require "cmdliner";;
 #require "core.top";;
 #require "ctypes";;
 #require "ctypes.stubs";;
+#require "ppx_compare";;
 #require "sawja";;
 #require "sqlite3";;
-#require "atdgen";;
 #require "xmlm";;
-#require "ANSITerminal";;
 
 open InferStdlib;;
 open InferGenerated;;
 open InferModules;;
+
+(* Most of infer uses this, useful for copy/pasting. Can be (partially) countered by typing `open
+Caml.Pervasives`. *)
+open IStd;;
+
+module L = Logging;;
+module F = Format;;