Add the SQLITE_TESTCTRL_RESULT_INTREAL test-control and use it to create
the intreal() SQL function in testfixture.  Write a few simple tests to
prove this all works.  TH3 will hold most of the INTREAL tests, probably.

FossilOrigin-Name: c9838731325e0ca73bd8784c10c74ae043fed7861e6de269fd90e29fa4a19955
diff --git a/src/main.c b/src/main.c
index 24f7f20..6358457 100644
--- a/src/main.c
+++ b/src/main.c
@@ -4104,6 +4104,22 @@
       break;
     }
 #endif /* defined(YYCOVERAGE) */
+
+    /*  sqlite3_test_control(SQLITE_TESTCTRL_RESULT_INTREAL, sqlite3_context*);
+    **
+    ** This test-control causes the most recent sqlite3_result_int64() value
+    ** to be interpreted as a MEM_IntReal instead of as an MEM_Int.  Normally,
+    ** MEM_IntReal values only arise during an INSERT operation of integer
+    ** values into a REAL column, so they can be challenging to test.  This
+    ** test-control enables us to write an intreal() SQL function that can
+    ** inject an intreal() value at arbitrary places in an SQL statement,
+    ** for testing purposes.
+    */
+    case SQLITE_TESTCTRL_RESULT_INTREAL: {
+      sqlite3_context *pCtx = va_arg(ap, sqlite3_context*);
+      sqlite3ResultIntReal(pCtx);
+      break;
+    }
   }
   va_end(ap);
 #endif /* SQLITE_UNTESTABLE */