Make sure the SQLITE_TCLAPI macro is always defined.

FossilOrigin-Name: f2f1323cc4d2ad2d6794dbfae8d50b747213e85d
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index c5b1ecc..35be76d 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -43,6 +43,14 @@
 */
 
 /*
+** Make sure the Tcl calling convention macro is defined.  This macro is
+** only used by test code and Tcl integration code.
+*/
+#ifndef SQLITE_TCLAPI
+#  define SQLITE_TCLAPI
+#endif
+
+/*
 ** Make sure that rand_s() is available on Windows systems with MSVC 2005
 ** or higher.
 */