fix: make code compile with updated V version

src/archive.c.v

@@ -4,7 +4,7 @@
 
 #include "archive.h"
 
-struct C.archive {}
+pub struct C.archive {}
 
 // Create a new archive struct for reading
 fn C.archive_read_new() &C.archive
@@ -71,7 +71,7 @@ fn C.archive_filter_code(&C.archive, int) int
 
 #include "archive_entry.h"
 
-struct C.archive_entry {}
+pub struct C.archive_entry {}
 
 // Create a new archive_entry struct
 fn C.archive_entry_new() &C.archive_entry

src/db/db.v

@@ -3,7 +3,7 @@ module db
 import sqlite
 import time
 
-struct VieterDb {
+pub struct VieterDb {
 	conn sqlite.DB
 }
 

src/package/package.v

@@ -4,7 +4,7 @@ import os
 import util
 
 // Represents a read archive
-struct Pkg {
+pub struct Pkg {
 pub:
 	path        string   [required]
 	info        PkgInfo  [required]