fix genfilelist

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

2005/.filelist

@@ -1,8 +1,8 @@
 2005/2005.tar.bz2
-2005/Makefile
-2005/README.md
 2005/.filelist
 2005/guidelines.txt
 2005/index.html
+2005/Makefile
+2005/README.md
 2005/rules.txt
 2005/.year