Merge branch 'release/0.4.2' into develop
New release cycle.
Minor changelog fixup
NetBSD: Consider include directory used for NetBSD as well.
NetBSD: Ignore harmless linker warnings, so check-release script can be used.
NetBSD: Fix, must set stack after calling "getcontext", or else "makecontext" crashes.
NetBSD: Must not release the current stack, but only the original allocation.
Apply the lessons learned by using generic fibers on NetBSD to all variants.
Pass CCFLAGS and LDFLAGS environment variables to C++ compiler and linker.
NetBSD: Changelog entry, it's supported in next release.
Massive developer manual updates for optimization based on SSA
Windows: Fix, no abiflags on Windows, check for attribute presence instead of version.
Windows: Make "2to3" execution portable.
Windows: For Python3 attempt to locate a Python2 to run Scons and use it.
Windows: Fix, do not insist on running Python as target Python
Python3: Fix, need to use bytes pattern, otherwise it's a type error.
Rename test, otherwise it clashes with "builtins" module on case insensitive filesystems.
Fix, take truth value before evaluating branches, otherwise it could be corrupted.

Practically this made no difference yet, as only nodes tell truth values that
are not impacted, but in the future this would cause bugs.
Store variable traces as objects.
Python3.3: The "__initializing__" module attribute shall not be set for main modules.