fix genfilelist

Fixed the sort for `make genfilelist` to ignore case
and to use the ${SORT} makefile variable.

1995/.filelist

@@ -1,10 +1,10 @@
 1995/1995.tar.bz2
-1995/Makefile
-1995/README.md
 1995/.filelist
 1995/.gitignore
 1995/guidelines.txt
 1995/index.html
+1995/Makefile
 1995/mkentry.c
+1995/README.md
 1995/rules.txt
 1995/.year