Makefile: clean-up spaces

In Makefile.Pl clean up spaces for consistency:
- replace tabs with spaces
- remove spaces at end of lines
- fix indent
Makefile: fix INSTALLDIRS for perl >= 5.12

Historically, dual-life modules have upgraded to the "perl"/"core"
installdirs (as opposed to site, where most modules go). This kind of
made sense before 5.12, when we made sense out of our default loading
order, but really doesn't anymore right now. We should make all dual
life modules install to site when installed from CPAN on 5.12+.

See https://rt.perl.org/rt3/Public/Bug/Display.html?id=116479
Update CHANGES and bump version to 0.43

TODO: set release date in CHANGES and release!
Makefile: fix MAJOR typo
Merge pull request #4 from dolmen/fix/INSTALLDIRS

Fix INSTALLDIRS for perl 5.12+