parser: struct names must be capitalized

compiler/main.v

@@ -678,7 +678,8 @@ fn (v mut V) add_v_files_to_compile() {
 			continue
 		}
 		mod_path := v.find_module_path(mod)
-		// If we are in default mode, we don't parse vlib .v files, but header .vh files in
+		// If we are in default mode, we don't parse vlib .v files, but
+		// header .vh files in
 		// TmpPath/vlib
 		// These were generated by vfmt
 /*

compiler/parser.v

@@ -606,6 +606,9 @@ fn (p mut Parser) struct_decl() {
 	if name.contains('_') && !p.pref.translated {
 		p.error('type names cannot contain `_`')
 	}
+	if !p.builtin_mod && !name[0].is_capital() {
+		p.error('struct names must be capitalized: `struct Foo {`, not `struct foo {`')
+	}	
 	if is_interface && !name.ends_with('er') {
 		p.error('interface names temporarily have to end with `er` (e.g. `Speaker`, `Reader`)')
 	}