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.
Guile-Cairo is complete, wrapping almost all of the Cairo API. It is
API stable, providing a firm base on which to do graphics
work. Finally, and importantly, it is pleasant to use. You get a
powerful and well-maintained graphics library with all of the benefits
of Scheme: memory management, exceptions, macros, and a dynamic
programming environment.
