v.parser: fix the error message position, for a struct Abc, that lacks a body (#23627)

vlib/v/parser/struct.v

@@ -65,7 +65,7 @@ fn (mut p Parser) struct_decl(is_anon bool) ast.StructDecl {
 	mut pre_comments := p.eat_comments()
 	no_body := p.tok.kind != .lcbr && p.tok.kind != .key_implements
 	if language == .v && no_body {
-		p.error('`${p.tok.lit}` lacks body')
+		p.error_with_pos('`${p.tok.lit}` lacks body', name_pos)
 		return ast.StructDecl{}
 	}
 	if name.len == 1 {

vlib/v/parser/tests/struct_no_body_err.out

@@ -0,0 +1,5 @@
+vlib/v/parser/tests/struct_no_body_err.vv:1:8: error: `struct` lacks body
+    1 | struct Lexer
+      |        ~~~~~
+    2 | 
+    3 | struct Token {

vlib/v/parser/tests/struct_no_body_err.vv

@@ -0,0 +1,10 @@
+struct Lexer
+
+struct Token {
+	token_u string
+}
+
+fn main() {
+	token := Token{"this is a token"}
+	println(token.token_u)
+}