Uwe Ligges has asked us to use gdal-config --libs only during the configuration
step, and only add gdal-config --dep-libs if that failed as it is done
in sf package.
The problem is that this will still not account for every type of system either,
as in windows using gdal-config --libs is not sufficient for a successful
compilation for instance.
In this package the configure step including configure.win is also derived
from the same configure.ac, using a single base Makevars.in for every
platform ensuring more maintainability as there is only one single source of
configure.ac for handling that, instead of handling multiple Makevars variants.
The configuration script also makes use of functions that reuses the same logic for multiple ran tests, ensuring consistency and maintainability as we handle repetitive code only once.
Those improvements makes these scripts much more succint and readable, also making use of autotools best practices as usage of their native macros such as AS_IF, AC_PATH_PROG, AC_LINK_IFELSE, PKG_CHECK_MODULES, which ensures cross platform compatibility.