I've done a little digging into the source code. I hope this helps. libapl.cc hasn't been changed since SVN 1712. It seems to me that it has not caught up to changes in other parts of the code.
From searching the entire source tree and browsing the SVN repository, it looks like the following changes in SVN 1713 have contributed to breaking libapl.cc: the definition of resolve_right() in Symbol.hh and SystemVariable.hh was changed to add the additional argument the removal of the definition of extract_and_keep() in class Token in Token.hh. - Paul Rockwell
