add missing declare
fix bad behavior if pngcairo is input as device
use a simpler call for hershey fonts
reimplement pgsave and pgpap
fix window creation
allow multiple non-xwin plots to be open at once
Merge branch 'pull-request' of https://github.com/joequant/PG2PLplot into joequant-pull-request
Fixed some declaration issues

* Fixed some declaration issues:
  * unused declared variables, unused module variables, missing implicit statement
Added two more implicit nones