refactor variable names according to changes in Pmodules/0.99.15 in build-scripts of group 'Tools'

Tools/gnuplot/build

@@ -1,16 +1,9 @@
 #!/usr/bin/env modbuild
 
 pbuild::add_to_group 'Tools'
-pbuild::set_source_url "https://sourceforge.net/projects/gnuplot/files/$P/$V/$P-$V.tar.gz"
-pbuild::set_docfiles 'Copyright' 'ChangeLog' 'NEWS' 'README'
 
-pbuild::configure() {
-	"${MODULE_SRCDIR}"/configure \
-		--prefix="${PREFIX}" \
-		--with-gif=no \
-		--with-tiff=no \
-		|| exit 1
-}
+pbuild::set_download_url "https://sourceforge.net/projects/gnuplot/files/$P/$V/$P-$V.tar.gz"
+pbuild::set_docfiles 'Copyright' 'ChangeLog' 'NEWS' 'README'
 
 pbuild::make_all