Enable shared memory support

Packages describing “shm” as local USE flag

Package “shm” Flag Description
net-voip/umurmur Enable shared memory support
media-libs/libafterimage Use MIT shared memory extention for X image transfer.
sci-geosciences/gpsd export gpsd over shared memory
media-libs/imlib2 Use MIT shared memory support for X image transfer
media-video/mplayer Enable support for shm

All packages providing a “shm” USE flag (2)