Add support for sys-libs/gdbm (GNU database libraries)

Packages describing “gdbm” as local USE flag

Package “gdbm” Flag Description
mail-filter/pyzor Enables the Gdbm back-end database engine for pyzord
mail-client/neomutt Enable GDBM (GNU dbm) backend for header caching
media-sound/pulseaudio-daemon Use sys-libs/gdbm to store PulseAudio databases. Recommended for desktop usage. This flag causes the whole package to be licensed under GPL-2 or later.
mail-client/mutt Enable sys-libs/gdbm database backend for header caching
net-firewall/fwknop Use sys-libs/gdbm to store fwknopd digest cache

All packages providing a “gdbm” USE flag (27)