Log Message:
Put distfiles into a fixed subdirectory across versions, instead of creating
each directory per version.

Before:

	% ls -rt /usr/pkgsrc/distfiles/xemacs-packages*/apel*
	/usr/pkgsrc/distfiles/xemacs-packages-1.9/apel-1.25-pkg.tar.gz
	/usr/pkgsrc/distfiles/xemacs-packages-1.10/apel-1.26-pkg.tar.gz
	/usr/pkgsrc/distfiles/xemacs-packages-1.12/apel-1.26-pkg.tar.gz
	/usr/pkgsrc/distfiles/xemacs-packages-1.11/apel-1.26-pkg.tar.gz

After:

	% ls -rt /usr/pkgsrc/distfiles/xemacs-packages*/apel*
	/usr/pkgsrc/distfiles/xemacs-packages/apel-1.25-pkg.tar.gz
	/usr/pkgsrc/distfiles/xemacs-packages/apel-1.26-pkg.tar.gz

Pointed out by Robert Elz, PR22085.