Changes

Assigned expected symbol versions to libXpm.so

The symbol versions defined in mapfile-vers were not used while linking
because the variable $(LD_OPTIONS_SO) is not exported to the linker.
This causes a compatibility issue with older software.

See https://www.illumos.org/issues/14574

Co-authored-by: Jean-Pierre André <jpandre@users.sourceforge.net>
 (commit: c025e8d)