Lower the stack usage of a few functions

In vm/compaction.cpp I rescoped some variables to lower the stack usage
from 592 to 560 bytes. I wasn't very successful with this. The stack
usage is larger than it looks because methods on the structures used
take an implicit this pointer and a reference to the data (so the data
has to live out it's full scope and can't be put in a register).

In vm/debug.cpp I made a large (1024 bytes) stack allocated buffer
simply dynamically allocated.

In vm/os-unix.cpp I rescoped signal handling structures to not coincide
with each other and reduced a very large (1024 bytes) amount of stack
usage to less than 500 bytes.
colors.xyz: implement CIE XYZ colors.
colors.xyy: implement CIE xyY colors.
colors: change article titles.
colors.luv: implement CIELUV colors.
colors.luv: fix for rgba.
colors: fix summary.txt.
colors.xyz: some refactoring.
colors.lab: implement CIELAB colors.
colors: adding some wikipedia links.
colors: more doc fixes.
io.binary.fast: le> and be> should be unsigned.
colors.lch: implement CIELCH colors.
io.backend.unix.multiplexors.select: some cleanup.
core-foundation.file-descriptors: some cleanup.
curl: bindings to libcurl.
math.transforms.bwt: cleaner to check last.
alien.enums: cleanup using.
vm: Fix compilation on Windows. Fixes #1086.
tools.coverage.testvocab: Fix help lint errors.