[typing] export code transformation category of Ghost_cfg

src/kernel_internals/typing/ghost_cfg.mli

@@ -19,3 +19,9 @@
 (*  for more details (enclosed in the file licenses/LGPLv2.1).            *)
 (*                                                                        *)
 (**************************************************************************)
+
+(** Checks that normal cfg is not altered by ghost statements.
+    Registered as a transformation category (that doesn't transform
+    anything but will complain if ghost cfg is ill-formed)
+*)
+val transform_category: File.code_transformation_category