This changes the buildlink3.mk files to use an include guard for the
recursive include. The use of BUILDLINK_DEPTH, BUILDLINK_DEPENDS,
BUILDLINK_PACKAGES and BUILDLINK_ORDER is handled by a single new
variable BUILDLINK_TREE. Each buildlink3.mk file adds a pair of
enter/exit marker, which can be used to reconstruct the tree and
to determine first level includes. Avoiding := for large variables
(BUILDLINK_ORDER) speeds up parse time as += has linear complexity.
The include guard reduces system time by avoiding reading files over and
over again. For complex packages this reduces both %user and %sys time to
half of the former time.
The Telepathy project is building a unified framework for many
different kinds of real-time communications. It uses the D-Bus
messaging system to provide a simple interface for client applications,
allowing them to quickly take advantage of Telepathy's benefits.
* Real-time: Telepathy supports instant messaging (both one-to-one
and in groups), voice calls and video calls; it's less suited for
store-and-forward applications like email
* Unified: Many different programs can take advantage of these
communications; Telepathy lets these programs work together
* Framework: Telepathy allows the different aspects of communication
handling to be divided between different parts of the system,
meaning each part is simpler
