SOSI - configure script

[shot2]

Request: With the recent availability of a SOSI library package (e.g. ​libfyba0 and libfyba-dev) in various Linux distributions, ./configure --with-sosi should attempt to locate the required dependencies in standard OS locations.

Issue: In its current state, the configure script contains detection logic which assumes that the SOSI library has been either manually built and installed under /usr/local/lib|include, or should get detected under $with_sosi/lib etc. Both solutions are likely to fail when using the OS-provided package in a multiarch environment.

Example of install location for libfyba0 package on a vanilla Ubuntu 16.04 amd64:

$ldconfig -p | grep libfy
        libfyut.so.0 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libfyut.so.0
        libfyut.so (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libfyut.so
        libfygm.so.0 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libfygm.so.0
        libfygm.so (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libfygm.so
        libfyba.so.0 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libfyba.so.0
        libfyba.so (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libfyba.so

N.B. Temporary workarounds: either hand-editing the configure script, or creating symlinks to the libraries/headers then use the '$with_sosi' configure option

[shot2]

As a sidenote, the current way of linking to SOSI libraries (libfy*.a) is prone to failure, due to nesting these 3 .a files directly within the static gdal library, without listing their objects.

*** Warning: Linking the shared library libgdal.la against the
*** static library /usr/lib/x86_64-linux-gnu/libfyba.a is not portable!

*** Warning: Linking the shared library libgdal.la against the
*** static library /usr/lib/x86_64-linux-gnu/libfygm.a is not portable!

*** Warning: Linking the shared library libgdal.la against the
*** static library /usr/lib/x86_64-linux-gnu/libfyut.a is not portable!

[Even Rouault]

trunk r34207 configure: improve detection of packaged libfyba (SOSI) --with-sosi, as in Ubuntu 16.04 (#6488)