Not quite a mass replacement as I've used OS X and Mac OS X where
describing specific older versions and added compatibility methods
for things in the DSL.
Substitue each Version.new and HeadVersion.new with Version.create
to unify Version and HeadVersion instantiation among core code.
Note that this does not relate to Mac::OS::Version class.
This reverts commit 85271644b0083cbc0fd6fea71120d1ad859fbc2a.
Alex noticed that setting PYTHONPATH causes weirdness if we depend_on
something which may be optionally built --with-python3; PYTHONPATH
unexpectedly contains python3 modules in the depending formula if
the formula upon which it depends was built --with-python3 even
though the depending formula may only use python2.
ClosesHomebrew/homebrew#43724. ClosesHomebrew/homebrew#43744.
Dependency is another similar, related class and it's super confusing
to have some Requirements that are named *Dependency.
ClosesHomebrew/homebrew#38891.
Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
