!!! existing preserved libs:
>>> package: app-pda/libusbmuxd-1.0.10
 *  - /usr/lib64/libusbmuxd.so.2
 *  - /usr/lib64/libusbmuxd.so.2.1.0
 *      used by /usr/bin/idevicepair (app-pda/libimobiledevice-1.1.6)
 *      used by /usr/lib64/libgpod.so.4.3.2 (media-libs/libgpod-0.8.3-r1)
 *      used by /usr/lib64/libimobiledevice.so.4.0.1 (app-pda/libimobiledevice-1.1.6)
 *      used by /usr/lib64/python2.7/site-packages/gpod/_gpod.so (media-libs/libgpod-0.8.3-r1)
Use emerge @preserved-rebuild to rebuild packages using these libraries