Begin adding the data-structure explaining subsystem.  All is contained within

FossilOrigin-Name: 79ae51c5b1b20ed0a425a87e65a32a096a80b7e1
diff --git a/src/main.c b/src/main.c
index 8562a90..ca98d31 100644
--- a/src/main.c
+++ b/src/main.c
@@ -2936,6 +2936,20 @@
       break;
     }
 
+    /*   sqlite3_test_control(SQLITE_TESTCTRL_EXPLAIN_STMT,
+    **                        sqlite3_stmt*,const char**);
+    **
+    ** If compiled with SQLITE_DEBUG, each sqlite3_stmt holds a string that
+    ** describes the optimized parse tree.  This test-control returns a
+    ** pointer to that string.
+    */
+    case SQLITE_TESTCTRL_EXPLAIN_STMT: {
+      sqlite3_stmt *pStmt = va_arg(ap, sqlite3_stmt*);
+      const char **pzRet = va_arg(ap, const char**);
+      *pzRet = sqlite3VdbeExplanation((Vdbe*)pStmt);
+      break;
+    }
+
   }
   va_end(ap);
 #endif /* SQLITE_OMIT_BUILTIN_TEST */