Make the multiplexor and the IntArray extensions callable from C++.

FossilOrigin-Name: cbd8fddf3b4cde840279502e1e9b151bb4bd42f0

src/test_intarray.h

@@ -76,6 +76,13 @@
 */
 #include "sqlite3.h"
 
+/*
+** Make sure we can call this stuff from C++.
+*/
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /*
 ** An sqlite3_intarray is an abstract type to stores an instance of
 ** an integer array.
@@ -112,3 +119,7 @@ int sqlite3_intarray_bind(
   sqlite3_int64 *aElements,      /* Content of the intarray */
   void (*xFree)(void*)           /* How to dispose of the intarray when done */
 );
+
+#ifdef __cplusplus
+}  /* End of the 'extern "C"' block */
+#endif