Building gnuplot5.2rc2 on linux mint mate

[Jim M. <jm...@ro...>]

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
qt5-default, libqt5svg5-dev,qttools5-dev,qttools-dev-tools,liblua5.2,lua5.2

I was then able to build and install gnuplot starting with ./configure 
--with-qt  --with-lua

/usr/lib/x86_64-linux-gnu/pkgconfig contained
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.

Jim