Tiny fixes for extractpdfmark

Tiny fixes for extractpdfmark

Individual changes:
1) Fix extractpdfmark not coming from PATH

If STEPMAKE_PROGS cannot find an optional program, it returns "false".
Checking for this value is better than requiring exactly "extractpdfmark"
which does not hold if the program is not in PATH and the user explicitly
sets the environment variable EXTRACTPDFMARK.

2) Fix extractpdfmark with GhostScript 9.50

GhostScript 9.50 defaults to -dSAFE, so the build system needs to pas
in -dNOSAFE explicitly.

3) Update message for optional extractpdfmark

From my experiments, enabling extractpdfmark rather increases the
required disk space. This is probably because the process produces
additional intermediate files. It only benefits the final PDF docs.

[lemzwerg, 2020-01-25 09:15:11]

LGTM, thanks

https://codereview.appspot.com/571420055/diff/571400046/configure.ac
File configure.ac (right):

https://codereview.appspot.com/571420055/diff/571400046/configure.ac#newcode391
configure.ac:391: ["(Using Ghostscript >= 9.20 together with Extract PDFmark"])
I suggest to use the program's name.

  s/Extract PDFmark/extractpdfmark/

[hahnjo, 2020-01-25 09:19:27]

https://codereview.appspot.com/571420055/diff/571400046/configure.ac
File configure.ac (right):

https://codereview.appspot.com/571420055/diff/571400046/configure.ac#newcode391
configure.ac:391: ["(Using Ghostscript >= 9.20 together with Extract PDFmark"])
On 2020/01/25 09:15:10, lemzwerg wrote:
> I suggest to use the program's name.
> 
>   s/Extract PDFmark/extractpdfmark/

I wasn't sure either, but https://github.com/trueroad/extractpdfmark says
"Extract PDFmark" it's the full name of the project. But maybe we should just
change it for consistency.

[hahnjo, 2020-01-26 20:22:37]

https://codereview.appspot.com/571420055/diff/571400046/configure.ac
File configure.ac (right):

https://codereview.appspot.com/571420055/diff/571400046/configure.ac#newcode391
configure.ac:391: ["(Using Ghostscript >= 9.20 together with Extract PDFmark"])
On 2020/01/25 09:19:27, hahnjo wrote:
> On 2020/01/25 09:15:10, lemzwerg wrote:
> > I suggest to use the program's name.
> > 
> >   s/Extract PDFmark/extractpdfmark/
> 
> I wasn't sure either, but https://github.com/trueroad/extractpdfmark says
> "Extract PDFmark" it's the full name of the project. But maybe we should just
> change it for consistency.

Do you want me to make this change? I don't have a strong opinion on this one, I
just left the name from the original message.

[Dan Eble, 2020-01-27 01:58:15]

On 2020/01/26 20:22:37, hahnjo wrote:
> Do you want me to make this change? I don't have a strong opinion on this one,
I
> just left the name from the original message.

In case a second opinion is useful, I'll give mine.  I see Werner's point, but I
also think the current name is clear enough, so I wouldn't blame you for leaving
it alone.

[lemzwerg, 2020-01-27 06:21:49]

> > Do you want me to make this change?
> > I don't have a strong opinion on this one,
> > I just left the name from the original message.
> 
> In case a second opinion is useful, I'll give mine.
> I see Werner's point, but I also think
> the current name is clear enough,
> so I wouldn't blame you for leaving it alone.

Given that packages for GNU/Linux distributions are rather called
`extractpdfmark` than `Extract PDFmark` you save people from doing one more
google search if you use the former.  So yes, I favour a change of the name.

[hahnjo, 2020-01-27 07:34:32]

rebase and adapt message