Fix decl c struct follow a v struct

struct C.CURL

struct Curl {
    h *C.CURL
}

compiler/parser.v

@@ -422,7 +422,7 @@ fn (p mut Parser) struct_decl() {
 		}
 	}
 	// V used to have 'type Foo struct', many Go users might use this syntax
-	if p.tok == STRUCT {
+	if !is_c && p.tok == STRUCT {
 		p.error('use `struct $name {` instead of `type $name struct {`')
 	}
 	// Register the type