overhaul of configure.ac

[Peter Johansson]

The current methods with *FLAGS is messy. Look at yat how to use APR macro.

The replacing gnuplot branch has modified configure.ac somewhat so wait with these changes until that branch has been merged.

[Jari Häkkinen]

Replying to peter:

The replacing gnuplot branch has modified configure.ac somewhat so wait with these changes until that branch has been merged.

Thanks.

[Peter Johansson]

(In [887]) refs #401

splitting LIBS *FLAGS into prefixes APR_ SVN_ and DEFAULT_ and modified configure end output to use these flags.

[Peter Johansson]

(In [888]) message should have been

Do not call pkg-config if it is not available, but just fail. Splitting plplot flags into libs ldflags and cppflags. Adding configure option --with-plplot.

[Peter Johansson]

(In [901]) refs #401 fixes #408

Modifications of detection of plplot;

• detection of plplot will not fail due to absent pkg-config
• if pkg-config is available and it finds pc file for plplot, then we use it to retrieve compiler/linker flags, otherwise we guess.
• new AC_DEFINE(HAVE_PLPLOT)
• configure now accepts --without-plplot (or --with-plplot=no) and tests are skipped (following build will currently not work)
• added a test linking against plplot library

[Peter Johansson]

(In [902]) fixes #401

It is now possible to build without plplot. It is even possible to generate reports, which obviously will be without images. If compiling and HAVE_PLPLOT is not defined, the Graph class becomes a lame empty class doing nothing (but existing). Needs some revision on README.