gnuplot: add recipe for version 5.2.0.
gnuplot: add recipe for version 5.2.0.

koletzky/haikuports,haikuports/haikuports,moochris/haikuports,nielx/haikuports,moochris/haikuports,haikuports/haikuports,miqlas/haikuports,haikuports/haikuports,haikuports/haikuports,nielx/haikuports,koletzky/haikuports,Begasus/haikuports,Begasus/haikuports,Begasus/haikuports,moochris/haikuports,Begasus/haikuports,miqlas/haikuports,haikuports/haikuports,nielx/haikuports,miqlas/haikuports,Begasus/haikuports,koletzky/haikuports