[dvipdfmx] Creation date and summer time

[Petr Krajník]

I found a problem when the datetime values are generated. As example the 
pdf creation datetime. These things are calculated in dpxutil.c function 
"dpx_util_format_asn_date". It gives the right date, time and time zone. 
So far ok. But we have now (in central Europe) summer time. One hour 
less. And this is not taken into account... All the values are shifted 
by one hour plus.

I think It should be taken into the calculation when time zone is made. 
 From the "tm" struct we can read the "tm_isdst" (daylight saving time) 
and if nonzero I would increment the time zone by one.

So we would get the right values when pdf readers shows dates.

Thank you.

Petr Krajník