The vvp/ivl_dlfcn.h and cadpli/ivl_dlfcn.h files are essentially the
same, but have diverged a bit over the years. Merge them into a single
shared file at the top level. Use the static prefix for all inline
functins (currently only used in the cadpli version) as that will fix
issue #1301. We now require the compiler to support at least C99, so
can use "inline", not "__inline__".
Martin Whitaker