... in Bison 2.3a, those forms seem to
already work.
Really? Not for me:
% ~/installs/bison/2.3a/bin/bison --skeleton="/tmp.m4" tmp.y
/usr/local/bin/m4: /home/jdenny/installs/bison/2.3a/share/bison//
tmp.m4: No such file or directory
/home/jdenny/installs/bison/2.3a/bin/bison: subsidiary program `/
usr/local/bin/m4' failed (exit status 1)
% ~/installs/bison/2.3a/bin/bison --skeleton="./tmp.m4" tmp.y
/usr/local/bin/m4: /home/jdenny/installs/bison/2.3a/share/bison/./
tmp.m4: No such file or directory
/home/jdenny/installs/bison/2.3a/bin/bison: subsidiary program `/
usr/local/bin/m4' failed (exit status 1)