* src/tgba/tgba.hh, src/tgba/tgba.cc (set_named_prop): Add a template
version.
(get_named_prop): Hide the old version, and supply a template version
that casts.
* src/bin/ltlcross.cc, src/hoaparse/hoaparse.yy, src/tgbaalgos/hoa.cc,
src/tgbaalgos/product.cc: Adjust usage.