I've tested release candidate 2 on systems running linux mint 17, 17.2,
17.3, and 18.2. I was able to install and use the qt and tikz terminals
on all systems.
Linux Mint Mate 18.2 was newly installed, and I attempted to find a
minimal set of extra dependencies. I installed the following:
mc and emacs with the Package Manager, for my convenience
subset of texlive 2017 (for testing tikz)
gpp and g++ with Package Manager, needed for build
I was then able to build and install gnuplot starting with ./configure
lua-5.2.pc -> lua5.2.pc and lua52.pc -> lua5.2.pc
It was not necessary to add a link to lua.pc as stated in INSTALL.