Allow overriding lp and lpr binary paths in PSPrintJob

[Rolf van Kleef]

I am not sure about whether this is the correct list for this, or whether this is an appropriate
message for this list, but I have been told to send an email here regarding a PR I submitted on
GitHub.

I recently ran into trouble with printing on Linux, where the lpr binary was on a non-standard path
(not in /usr/bin/lpr). After looking in the code, I found out that this path cannot be overridden.
It seems that such paths should be able to be overriden, and so, I propose to add a system property
named "sun.print.lprPath" and "sun.print.lpPath" to override these paths. See the PR below.

https://github.com/openjdk/jdk/pull/6052

Regards,
Rolf van Kleef