Fix wav append mode (bug #3498)

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@4958 65c4cc65-6c06-0410-ace0-fbb531ad65f3

file.c

@@ -855,8 +855,12 @@ struct ast_filestream *ast_writefile(const char *filename, const char *type, con
 		return NULL;
 	}
 	/* set the O_TRUNC flag if and only if there is no O_APPEND specified */
-	if (!(flags & O_APPEND)) 
+	if (flags & O_APPEND) { 
+		/* We really can't use O_APPEND as it will break WAV header updates */
+		flags &= ~O_APPEND;
+	} else {
 		myflags = O_TRUNC;
+	}
 	
 	myflags |= O_WRONLY | O_CREAT;