Add threads support for various packages. Usually pthreads

Packages describing “threads” as local USE flag

Package“threads” Flag Description
app-editors/emacsAdd elisp threading support
dev-libs/xerces-cEnable threading support through pthread (or other libraries on AIX, IRIX, HPUX, Solars). Highly recommended
dev-libs/xmlrpc-cControls whether to build the Abyss web-server with pthreads or fork 'threading'.
dev-scheme/racketEnable support for green threads
media-plugins/gkrellmpcUse separate thread to init connection (unsafe)
net-proxy/privoxyEnable POSIX threads. Highly recommended, otherwise both build and run-time features may not work properly.

All packages providing a “threads” USE flag (97)