more misuse of G_GNUC_CONST

[Darin Adler <darin bentspoon com>]

g_int_equal and g_int_hash are marked G_GNUC_CONST. This is incorrect 
because you can call them twice with the same values and get different 
results if the pointed-to values are different.

g_directory_hash and g_direct_equal are correctly marked G_GNUC_CONST.

I would have put this into a bug report, but I can't reach bugzilla.gnome.
org right now.

    -- Darin