Remove build_identifier from the public_interface

This is not used outside of the ssa_exprt class and shouldn't
be part of the public interface.

Author: romainbrenguier

src/util/ssa_expr.cpp

@@ -82,7 +82,7 @@ bool ssa_exprt::can_build_identifier(const exprt &expr)
     return false;
 }
 
-std::pair<irep_idt, irep_idt> ssa_exprt::build_identifier(
+static std::pair<irep_idt, irep_idt> build_identifier(
   const exprt &expr,
   const irep_idt &l0,
   const irep_idt &l1,

src/util/ssa_expr.h

@@ -121,12 +121,6 @@ class ssa_exprt:public symbol_exprt
 
   void update_identifier();
 
-  static std::pair<irep_idt, irep_idt> build_identifier(
-    const exprt &src,
-    const irep_idt &l0,
-    const irep_idt &l1,
-    const irep_idt &l2);
-
   /* Used to determine whether or not an identifier can be built
    * before trying and getting an exception */
   static bool can_build_identifier(const exprt &src);