I'm not sure this is a good idea because other functions might be
pulled from malloc.h, or malloc() might be find in yet another header.
It's nearly impossible to know, you would need to be familiar
with every system function used by libltdl and where it resides
on every system known to man. I think it is sufficient to do this
without the error message. Really, I can't be sure that making the
change from including both to including stdlib.h only won't break
some system somewhere, but it probably won't.