Get the installation prefix from the program dir. We have code
to obtain the directory where the executable resides for all
platforms we support, Linux, BSDs, Apple, etc.
On less well-known platforms where this isn't true (POSIX does not
define any standard interfaces for this) we fallback on
using a hard-coded installation prefix, like we have been doing
until now.
The path relocation allows the whole installation tree to be moved
without having to recompile the program. But note there are other
requirements for shared libraries to have full support for relocation.
This is only partial support.
We now use a header to pass the relative path definitions to avoid
excessively long compilation command lines as the number of #defines
increases.
João Valverde