toke.c: Add comment
Make /[\N{}-\N{}]/ match Unicodely on EBCDIC

This makes [\N{U+06}-\N{U+09}] match U+06, U+07, U+08, U+09 even on
EBCDIC platforms, allowing one to write portable ranges.  For 1047
EBCDIC this would match 0x2E, 0x2F, 0x16, and 0x05.

Thanks to Yaroslave Kuzmin for finding a bug in an earlier incarnation
of this patch.