Xfree86-4.1 no compose key possible

[Armin Wegner <wegner@ldv35.uni-trier.de>]

Hi,

I'm running kernel 2.4.18pre1 with testing.
I cannot compose characters with Multi_key in Xfree86 4.1.
I have got a Multi_key according to xev

KeyPress event, serial 23, synthetic NO, window 0xe00001,
    root 0x58, subw 0x0, time 1386270115, (103,176), root:(245,318),
    state 0x0, keycode 116 (keysym 0xff20, Multi_key), same_screen YES,
    XLookupString gives 0 characters:  ""

/etc/X11/XF86Config-4 says

Section "InputDevice"
        Identifier      "Generic Keyboard"
        Driver          "keyboard"
        Option          "CoreKeyboard"
        Option          "XkbRules"      "xfree86"
        Option          "XkbModel"      "pc105"
        Option          "XkbLayout"     "us"
EndSection

I would like to create the german a umlaut with <Multi_key><"><a> as it
has always been the way before reinstalling after a hard drive crash.

What's wrong? What's missing? Where can I find documentation about all
those options for the keyboard section?

Armin