Make central-data-structures a subpage of the architecture page

In order to prevent it being included at the root level of the
documentation site.

Author: thomasspriggs

doc/architectural/cbmc-architecture.md

@@ -61,7 +61,7 @@ transformation tools (see \ref other-tools).
 
 For an explanation of the data structures involved in the modeling of a GOTO
 program (the GOTO Intermediate Representation used by CBMC and assorted tools)
-please have a look [here](central-data-structures.md).
+please see \subpage central-data-structures .
 
 ## {C, java bytecode} → Parse tree → Symbol table → GOTO programs → GOTO program transformations → BMC → counterexample (goto_tracet) → printing ##
 

doc/architectural/central-data-structures.md

@@ -1,3 +1,7 @@
+\ingroup module_hidden
+
+\page central-data-structures Central Data Structures
+
 # Central Data Structures
 
 The following is some light technical documentation of the major data structures