* libltdl/ltdl.c: make all global strings char[], not char*; check

* libltdl/ltdl.c: make all global strings char[], not char*; check
that all calls to malloc() are properly cast
(strdup, strchr, strrchr, trim, free_vars): declare as inline
(find_module): allocate filename dynamically; support null dir
(free_vars): free dir and name only if non-null
(lt_dlopen): keep dir as NULL if not given; fix expression that
calculated the size of name; only free and name if non-null
(lt_dlopenext): allocate tmp dynamically