[mapserver-dev] heads up on gd,png,gif and jpeg build changes

[thomas bonfort]

Hi devs,
In order to resolve [1] and less importantly [2], I have made some non
trivial changes to the logic used inside the configure script when
looking for libpng, libjpeg, giflib and libgd. For the first three, we
now try to link against the libraries instead of explicitely looking
for libxxx.so in a set of predefined locations. For libgd, we now look
for the gdlib-config utility.
This might cause some minor issues with existing build scripts, which
I hope I can quickly iron out if you report them here or in a new
ticket.

cheers,
thomas

[1] https://github.com/mapserver/mapserver/issues/4315
[2] https://github.com/mapserver/mapserver/issues/386