search for: soext

This also defines SOEXT as the extension of shared objects (ie. "so" or "dll"), and uses it everywhere. I assumed this must already be defined by either autoconf or mingw (like OBJEXT) but I cannot find anything except in glib (G_MODULE_SUFFIX). Thanks: Zebediah Figura for helping out with exec vs sp...

Also available here: https://github.com/rwmjones/nbdkit/tree/2020-windows-mingw-nolib After a lot of work I have made the port to Windows work without using a separate library. Instead, on Windows only, we build an "import library" (library of stubs) which resolves references to nbdkit_* functions in the main program and fixes up the plugin, basically the first technique outlined in