Fix strncpy usage in botlib

All usage of strncpy in botlib should now either set string
terminator or use Q_strncpyz.

code/botlib/l_precomp.c

@@ -1323,7 +1323,7 @@ define_t *PC_DefineFromString(char *string)
 	script = LoadScriptMemory(string, strlen(string), "*extern");
 	//create a new source
 	Com_Memset(&src, 0, sizeof(source_t));
-	strncpy(src.filename, "*extern", sizeof(src.filename) - 1);
+	Q_strncpyz(src.filename, "*extern", sizeof(src.filename));
 	src.scriptstack = script;
 #if DEFINEHASHING
 	src.definehash = GetClearedMemory(DEFINEHASHSIZE * sizeof(define_t *));