greek-style quotes for greek input method?

[Giorgos Keramidas <keramida@ceid.upatras.gr>]

Greek books use a different set of quotes from the normal English
"double" or ``double'' quotes.  The default "el" input method of XKB and
my Gnome desktop maps these special greek-style quotes to the ";<" and
";>" input strings.  So when I switch to the Gnome-greek input method by
typing Alt-Shift I can type this text

    EL:  Ελληνικό κείμενο με   «εισαγωγικά».
    EN:  Greek    text    with «quotes».

by typing the greek-style quotes as ";<" and ";>" respectively.

The `greek' input method of Emacs supports most of the diacritic marks
with the following special key sequences:

    KEY SEQUENCE
    ------------
    You can also input more characters by the following key sequences:
    key char  [type a key sequence to insert the corresponding character]
    --- ---- --- ---- --- ---- --- ---- --- ---- --- ---- --- ---- --- ---- --- ---- --- ---- --- ----
    :I  Ϊ    :i  ϊ    ;A  Ά    ;H  Ή    ;O  Ό    ;Y  Ύ    ;e  έ    ;i  ί    ;v  ώ    :;i ΐ    ;:i ΐ
    :Y  Ϋ    :y  ϋ    ;E  Έ    ;I  Ί    ;V  Ώ    ;a  ά    ;h  ή    ;o  ό    ;y  ύ    :;y ΰ    ;:y ΰ

It would be nice if it also supported ;< and ;> for greek-style quotes
but I don't know how to do this using the current sources of the file
`emacs/trunk/leim/quail/greek.el'.

Does anyone feel like showing me how to do this, or even patching
`quail/greek.el' directly?

The mapping that we could use from input text to Unicode character of
the greek-style quotes would be:

    (";<" "«")
    (";>" "»")