v.ast,v.fmt: support attributes on FnTypeDecl too

vlib/v/ast/ast.v

@@ -1152,6 +1152,7 @@ pub:
 	pos      token.Pos
 	type_pos token.Pos
 	comments []Comment
+	attrs    []Attr // attributes of type declaration
 }
 
 // TODO: handle this differently

vlib/v/fmt/fmt.v

@@ -1290,6 +1290,7 @@ pub fn (mut f Fmt) alias_type_decl(node ast.AliasTypeDecl) {
 }
 
 pub fn (mut f Fmt) fn_type_decl(node ast.FnTypeDecl) {
+	f.attrs(node.attrs)
 	if node.is_pub {
 		f.write('pub ')
 	}

vlib/v/fmt/tests/fn_type_attributes_and_calling_convention_keep.vv

@@ -0,0 +1,10 @@
+[callconv: 'stdcall']
+fn C.DefWindowProc(hwnd int, msg int, lparam int, wparam int)
+
+[callconv: 'stdcall']
+type FastFn = fn (int) bool
+
+[callconv: 'fastcall']
+fn zzz(x int, y int) int {
+	return x + y * 2
+}

vlib/v/parser/parser.v

@@ -3579,6 +3579,8 @@ fn (mut p Parser) type_decl() ast.TypeDecl {
 		p.table.sym(fn_type).is_pub = is_pub
 		type_pos = type_pos.extend(p.tok.pos())
 		comments = p.eat_comments(same_line: true)
+		attrs := p.attrs
+		p.attrs = []
 		return ast.FnTypeDecl{
 			name: fn_name
 			is_pub: is_pub
@@ -3586,6 +3588,7 @@ fn (mut p Parser) type_decl() ast.TypeDecl {
 			pos: decl_pos
 			type_pos: type_pos
 			comments: comments
+			attrs: attrs
 		}
 	}
 	sum_variants << p.parse_sum_type_variants()