Fix harmless compiler warnings on x64 MSVC, mostly in test code, but also in

tclsqlite.c and in the FTS4 module.

FossilOrigin-Name: 3281972eaa46cb57fd9f0387063f47430dc0a3b4

src/test3.c

@@ -80,7 +80,7 @@ static int btree_open(
     sDb.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_RECURSIVE);
     sqlite3_mutex_enter(sDb.mutex);
   }
-  n = strlen(argv[1]);
+  n = (int)strlen(argv[1]);
   zFilename = sqlite3_malloc( n+2 );
   if( zFilename==0 ) return TCL_ERROR;
   memcpy(zFilename, argv[1], n+1);