Fix util/mkerr.pl

- Adjust mkerr.pl to produce the line length we used for source
  reformating.

- Have mkerr.pl keep track of preprocessor directive indentation

  Among others, do not spuriously throw away a #endif at the end of
  header files.

- Make sure mkerr.pl specifies any header inclusion correctly

Reviewed-by: Rich Salz <rsalz@openssl.org>