New comment by TOertel on void-packages repository

https://github.com/void-linux/void-packages/issues/12035#issuecomment-498241816
Comment:
I was referring to the different behaviors, alpha not working in png, jpeg and x11.  I have no evidence that this is "intended behavior".

So, for now, I've opened an upstream bug: https://sourceforge.net/p/gnuplot/bugs/2177