misc/54128: Unify PYTHON_VERSION_DEFAULT and PYTHON_DEFAULT_VERSION

[ben@pocket.services]

>Number:         54128
>Category:       misc
>Synopsis:       Unify PYTHON_VERSION_DEFAULT and PYTHON_DEFAULT_VERSION
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    misc-bug-people
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Fri Apr 19 11:55:00 +0000 2019
>Originator:     Benjamin Lorenz
>Release:        NetBSD 8.99.37
>Organization:
	
>Environment:
	
	
System: NetBSD chaos.lorenz.place 8.99.37 NetBSD 8.99.37 (GENERIC) #1: Sat Apr 13 15:21:14 CEST 2019 bjjl@chaos.lorenz.place:/home/bjjl/8.99/obj/sys/arch/amd64/compile/GENERIC amd64
Architecture: x86_64
Machine: amd64
>Description:
Seems some packages in pkgsrc listen to PYTHON_VERSION_DEFAULT,
whereas https://www.netbsd.org/docs/pkgsrc/configuring.html
speaks of PYTHON_DEFAULT_VERSION.

Not sure these are not just typos, but if not, then we should make sure
the configuration variable is the same all over the place.

>How-To-Repeat:
	
>Fix:
	

>Unformatted: