#2728 gnuplot-6.0.1: missing dnl comment marker in configure.ac

[Ulrich Müller]

checking for CAIROPDF... yes
checking for CAIROEPS... yes
checking for WEBP... yes
./configure: line 16960: Enable: command not found

The line is missing the initial dnl. It is present in master, but not in branch-6-0-stable (apparently it was accidentally dropped in commit 21a0dfd8b5a749390fb11821ca9cc54d77280a38).

Trivial patch is attached.

[Ethan Merritt]

Thanks