#345 documentation of WITH_PLPLOT in perldl.conf incorrect

[Edward Baudrez]

In perldl.conf, the line that says

WITH_PLPLOT => 0, # Leave it up to PDL to decide

(0 there by default) has incorrect documentation: 0 will not build PLplot support (even if everything is available on the build host to build PLplot). You have to set it to 1 to have PLplot support built, so what the documentation suggests is misleading.

[Chris Marshall]

The PLplot support was disabled since for a while,
it would not build. It is definitely confusing with the
comment as remaining.