atlas portage # emerge -auDNvp @world

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild     U  ] app-office/libreoffice-l10n-5.2.3.3::gentoo [5.1.4.2::gentoo] USE="-offlinehelp" L10N="-af -am -ar -as -ast -be -bg -bn -bn-IN -bo -br -brx -bs -ca -ca-valencia -cs -cy -da -de -dgo -dz -el -en -en-GB -en-ZA -eo -es -et -eu -fa -fi -fr -ga -gd -gl -gu -gug -he -hi -hr -hu -id -is -it -ja -ka -kk -km -kmr-Latn -kn -ko -kok -ks -lb -lo -lt -lv -mai -mk -ml -mn -mni -mr -my -nb -ne -nl -nn -nr -nso -oc -om -or -pa -pl -pt -pt-BR -ro -ru -rw -sa -sat -sd -si -sid -sk -sl -sq -sr -sr-Latn -ss -st -sv -sw-TZ -ta -te -tg -th -tn -tr -ts -tt -ug -uk -uz -ve -vi -xh -zh-CN -zh-TW -zu" 0 KiB
[ebuild     U  ] dev-libs/icu-58.1-r1:0/58.1::gentoo [57.1:0/57::gentoo] USE="-debug -doc -examples -static-libs" ABI_X86="32 (64) (-x32)" 22,819 KiB
[ebuild     UD ] app-emulation/virtualbox-modules-4.3.38::gentoo [5.1.8::gentoo] USE="-pax_kernel" 532 KiB
[ebuild     U  ] dev-libs/libixion-0.11.1:0/0.11::gentoo [0.9.0:0/0.10::gentoo] USE="python%* -static-libs" PYTHON_SINGLE_TARGET="python3_4%* (-python3_5)" PYTHON_TARGETS="python3_4%* (-python3_5) (-python2_7%*)" 359 KiB
[ebuild     U  ] dev-libs/liborcus-0.11.2:0/0.11::gentoo [0.9.2-r1:0/0.10::gentoo] USE="python%* spreadsheet-model -static-libs -tools" PYTHON_SINGLE_TARGET="python3_4%* (-python3_5)" PYTHON_TARGETS="python3_4%* (-python3_5)" 1,590 KiB
[ebuild     U  ] app-office/libreoffice-bin-5.2.3.3::gentoo [5.1.4.2::gentoo] USE="(-aqua) -gnome -java -kde" PYTHON_SINGLE_TARGET="python2_7 -python3_4 (-python3_5)" PYTHON_TARGETS="python2_7 python3_4 (-python3_5)" 74,941 KiB
[ebuild     UD ] app-emulation/virtualbox-bin-4.3.38.106717::gentoo [5.1.8.111374::gentoo] USE="additions chm python -debug -headless -rdesktop-vrdp -sdk -vboxwebsrv" PYTHON_TARGETS="python2_7" 93,638 KiB
[ebuild  N     ] gnome-base/gnome-keyring-3.20.0::gentoo  USE="caps filecaps pam ssh-agent (-selinux) {-test}" 0 KiB
[ebuild     U  ] www-client/chromium-55.0.2883.75::gentoo [54.0.2840.100::gentoo] USE="cups (gn) hangouts (pic) proprietary-codecs pulseaudio suid system-ffmpeg tcmalloc widevine -custom-cflags -gnome -gnome-keyring (-gtk3) -kerberos (-neon) (-selinux) {-test}" L10N="am ar bg bn ca cs da de el en-GB es es-419 et fa fi fil fr gu he hi hr hu id it ja kn ko lt lv ml mr ms nb nl pl pt-BR pt-PT ro ru sk sl sr sv sw ta te th tr uk vi zh-CN zh-TW" 0 KiB
[ebuild   R    ] app-text/texlive-2014::gentoo  USE="X context epspdf games pdfannotextractor png science texi2html truetype xml -cjk -detex -dvi2tty -extra* -graphics -humanities -jadetex -luatex -metapost -music -omega -pstricks -publishers -tex4ht -xetex -xindy" L10N="-af -ar -as -bg -bn -br -ca -cs -cy -da -de -el -en -en-GB -eo -es -et -eu -fa -fi -fr -ga -gl -gu -he -hi -hr -hsb -hu -hy -ia -id -is -it -ja -kn -ko -la -lo -lt -lv -ml -mn -mr -nb -nl -nn -no -or -pa -pl -pt -rm -ro -ru -sa -sco -sk -sl -sq -sr -sv -ta -te -th -tk -tr -uk -vi -zh" 0 KiB

Total: 10 packages (6 upgrades, 2 downgrades, 1 new, 1 reinstall), Size of downloads: 193,877 KiB

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

dev-libs/icu:0

  (dev-libs/icu-58.1-r1:0/58.1::gentoo, ebuild scheduled for merge) pulled in by
    dev-libs/icu:0/58.1 required by (app-office/libreoffice-bin-5.2.3.3:0/0::gentoo, ebuild scheduled for merge)
                ^^^^^^^

  (dev-libs/icu-57.1:0/57::gentoo, installed) pulled in by
    >=dev-libs/icu-51.2-r1:0/57=[abi_x86_32(-),abi_x86_64(-)] required by (dev-libs/libxml2-2.9.4:2/2::gentoo, installed)
                          ^^^^^^
    (and 16 more with the same problem)

NOTE: Use the '--verbose-conflicts' option to display parents omitted above

It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously.  If such a conflict exists in
the dependencies of two different packages, then those packages can
not be installed simultaneously. You may want to try a larger value of
the --backtrack option, such as --backtrack=30, in order to see if
that will solve this conflict automatically.

For more information, see MASKED PACKAGES section in the emerge man
page or refer to the Gentoo Handbook.