gdk_posix: don't export declarations outside of GDK_POSIX guard
gdk_posix: don't export declarations outside of GDK_POSIX guard

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb