Consolidate NEWS file for 4.9.0

Signed-off-by: Moritz Heidkamp <moritz@twoticketsplease.de>
Improve GC performance by avoiding tracking of nursery->nursery or heap->heap mutations.

Instead, we only track mutations pointing *into* the nursery,
and only on objects *not* in the nursery.

Signed-off-by: Mario Domenech Goulart <mario.goulart@gmail.com>
Remove stuff from posixwin's 'unimplemented' list which has since been implemented
Make sure "ev-tstvec" does not hold on to a released object, because the storage may be re-used during GC.

This would magically turn the released (and probably mangled) data into a heap-object again, should the heap be
resized.

Signed-off-by: Peter Bex <peter.bex@xs4all.nl>
Signed-off-by: Mario Domenech Goulart <mario.goulart@gmail.com>
NEWS: typo fix (s/leightweight/lightweight/)
Bump C_MINOR_VERSION to 9
Bump version to 4.9.1
Add tests/version-tests.scm

Basic version tests.  Check if chicken-version matches the values for
C_MAJOR_VERSION/C_MINOR_VERSION and the registered
chicken-<major>.<minor> feature.

Signed-off-by: Peter Bex <peter.bex@xs4all.nl>