Don't normalize the open mode for popen()

popen() does not accept all the normal modes... especially on
Linux which doesn't even allow the default "r+" mode.

Suck it penguin heads.

exec/tests/file/popen.js

+if (system.platform == 'Win32')
+	exit();
+
+let f = new File("/bin/ls");
+if (!f.popen("r"))
+	throw new Error(`popen() failed! {f.error}`);
+while(f.is_open) {
+	let l = f.readln();
+	if (!l)
+		f.close();
+}

src/sbbs3/js_file.cpp

@@ -386,7 +386,9 @@ js_popen(JSContext *cx, unsigned argc, JS::Value *arglist)
 	mode = "r+"; /* default mode */
 	if (!js_argc(cx, args, "su", &mode, &bufsize))
 		return false;
-	normalizemode(cx, mode.c_str(), fpt->mode, sizeof(fpt->mode), NULL, NULL);
+	// Don't normalize the mode... extra flags are not valid here.
+	//normalizemode(cx, mode.c_str(), fpt->mode, sizeof(fpt->mode), NULL, NULL);
+	SAFECOPY(fpt->mode, mode.c_str());
 
 	fpt->fp = popen(fpt->name, fpt->mode);
 	if (fpt->fp != NULL) {