This refers to 3 lines removed during an XFree86 merge.  The change was done here:
http://cgit.freedesktop.org/xorg/lib/libX11/diff/src/xkb/XKBBind.c?id=c6349f43193b74a3c09945f3093a871b0157ba47

These are the three lines that need to be re-added to XKBind.c in XkbTranslateKeySym:
    if (_XkbUnavailable(dpy))
        return _XTranslateKeySym(dpy, *sym_rtrn, mods, buffer, nbytes);
    _XkbCheckPendingRefresh(dpy,dpy->xkb_info);

Before running the testcase, make sure that a Russian font is installed on your X Server and the Caps Lock KeySym is set up as follows:
CapsLock:  Unshifted=Mode_switch, Shifted=NoSymbol, Mode Switch=NoSymbol, Shift Mode Switch=NoSymbol

To run foo (it is attached):
1) Set up the Russian font on the X Server as explained in the above paragraph.
2) Run foo - you will see Cyrillic characters at start.  Hitting shift will show large Cyrillic characters.
3) Hit CapsLock - you will see large English characters when small English characters should be there.  This works on Solaris.

Basically, a CapsLock KeySym set to Unshifted=Mode_switch should default to a lower case character.  All characters are upper at present.