cgen: handle C typedefs

vlib/v/gen/cgen.v

@@ -159,9 +159,12 @@ pub fn (g mut Gen) typ(t table.Type) string {
 	if styp.starts_with('C__') {
 		styp = styp[3..]
 		if sym.kind == .struct_ {
+			info := sym.info as table.Struct
+			if !info.is_typedef {
 				styp = 'struct $styp'
 			}
 		}
+	}
 	if table.type_is(t, .optional) {
 		styp = 'Option_' + styp
 		if !(styp in g.optionals) {

vlib/v/parser/parser.v

@@ -1475,6 +1475,7 @@ fn (p mut Parser) struct_decl() ast.StructDecl {
 		p.next() // C
 		p.next() // .
 	}
+	is_typedef := p.attr == 'typedef'
 	mut name := p.check_name()
 	mut default_exprs := []ast.Expr
 	// println('struct decl $name')
@@ -1544,6 +1545,7 @@ fn (p mut Parser) struct_decl() ast.StructDecl {
 		name: name
 		info: table.Struct{
 			fields: fields
+			is_typedef: is_typedef
 		}
 	}
 	mut ret := 0

vlib/v/table/atypes.v

@@ -539,6 +539,7 @@ pub fn (kinds []Kind) str() string {
 pub struct Struct {
 pub mut:
 	fields []Field
+	is_typedef bool // C. [typedef]
 }
 
 pub struct Enum {