root@jmg:~#  emerge --prune --pretend

>>> These are the packages that would be unmerged:

 sys-devel/automake
    selected: 1.5 1.8.5-r3 1.6.3 1.7.9-r1 1.4_p6
   protected: 1.9.6-r2
     omitted: none

 x11-libs/gtk+
    selected: 1.2.10-r11
   protected: 2.8.19
     omitted: none

 dev-libs/glib
    selected: 2.10.3
   protected: 1.2.10-r5
     omitted: none

 sys-devel/autoconf
    selected: 2.13
   protected: 2.59-r7
     omitted: none