checker: improve pub struct check (fix #14446) (#14777)

vlib/net/address_linux.c.v

@@ -2,7 +2,7 @@ module net
 
 const max_unix_path = 108
 
-struct C.addrinfo {
+pub struct C.addrinfo {
 mut:
 	ai_family    int
 	ai_socktype  int
@@ -14,28 +14,28 @@ mut:
 	ai_next      voidptr
 }
 
-struct C.sockaddr_in {
+pub struct C.sockaddr_in {
 mut:
 	sin_family u16
 	sin_port   u16
 	sin_addr   u32
 }
 
-struct C.sockaddr_in6 {
+pub struct C.sockaddr_in6 {
 mut:
 	sin6_family u16
 	sin6_port   u16
 	sin6_addr   [4]u32
 }
 
-struct C.sockaddr_un {
+pub struct C.sockaddr_un {
 mut:
 	sun_family u16
 	sun_path   [max_unix_path]char
 }
 
 [_pack: '1']
-struct Ip6 {
+pub struct Ip6 {
 	port      u16
 	flow_info u32
 	addr      [16]u8
@@ -43,7 +43,7 @@ struct Ip6 {
 }
 
 [_pack: '1']
-struct Ip {
+pub struct Ip {
 	port u16
 	addr [4]u8
 	// Pad to size so that socket functions
@@ -54,12 +54,12 @@ struct Ip {
 	sin_pad [8]u8
 }
 
-struct Unix {
+pub struct Unix {
 	path [max_unix_path]u8
 }
 
 [_pack: '1']
-struct Addr {
+pub struct Addr {
 pub:
 	f    u16
 	addr AddrData