libga68/ChangeLog:
* configure.ac: New test to determine if symbol versioning is
supported.
* Makefile.am: Use result of above test to add appropriate linker
flags.
* Makefile.in: Regenerated.
* aclocal.m4: Likewise.
* configure: Likewise.
* ga68.map: New file.
* libtool-version: New file.
Signed-off-by: Pietro Monteiro <pietro@sociotechnical.xyz>