od: improve handling of padding

od: improve handling of padding

* src/od.c (decode_one_format): Alter the format, again.
(FMT_BYTES_ALLOCATED): Reduce size by adjusting to new format.
(MAX_INTEGRAL_TYPE_SIZE): Move earlier in the file.
(charname): Turn it into a 2D array, since there's no need for
pointers now.
(PRINT_TYPE, print_named_ascii, print_ascii): Add a width
parameter.
(write_block): Account for width parameter.
Using ideas from Paul Eggert.