This helps to export correct APIs for compiler toolchain which
does not support version script file. For example, mingw clang.
The APIs in libpulse.def are similar with map-file except those
are in pulse-simple and pulse-mainloop-glib. Those are exported
in different shared library in Windows platform.
Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/761>