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.
The Emacs shell sets $EMACS to "t" for detection purposes, but it causes
builds to fail when they attempt to call Emacs using the variable.
FixesHomebrew/homebrew-emacs#30.
ClosesHomebrew/homebrew#45495.
Signed-off-by: Alex Dunn <dunn.alex@gmail.com>
