macro_rules! dlopen_external_library {
(__struct, $structname: ident,
$(statics: $($sname: ident: $stype: ty),+,)|*
$(functions: $(fn $fname: ident($($farg: ty),*) -> $fret:ty),+,)|*
$(varargs: $(fn $vname: ident($($vargs: ty),+) -> $vret: ty),+,)|*
) => { ... };
(__impl, $structname: ident,
$(statics: $($sname: ident: $stype: ty),+,)|*
$(functions: $(fn $fname: ident($($farg: ty),*) -> $fret:ty),+,)|*
$(varargs: $(fn $vname: ident($($vargs: ty),+) -> $vret: ty),+,)|*
) => { ... };
($structname: ident,
$(statics: $($sname: ident: $stype: ty),+,)|*
$(functions: $(fn $fname: ident($($farg: ty),*) -> $fret:ty),+,)|*
$(varargs: $(fn $vname: ident($($vargs: ty),+) -> $vret: ty),+,)|*
) => { ... };
}