Import cargo type orders patch

https://www.tt-forums.net/viewtopic.php?p=1047749#p1047749

Port to current trunk, resolve various conflicts, etc.
Adjust bit allocations for CmdModifyOrder.
Use save_ext framework for added order flags.

src/saveload/extended_ver_sl.cpp

@@ -45,6 +45,8 @@ std::vector<uint32> _sl_xv_discardable_chunk_ids;           ///< list of chunks
 static const uint32 _sl_xv_slxi_chunk_version = 0;          ///< current version os SLXI chunk
 
 const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
+	{ XSLFI_CARGO_TYPE_ORDERS,      XSCF_NULL,                1,   1, "cargo_type_orders",         NULL, NULL, NULL        },
+
 	{ XSLFI_NULL, XSCF_NULL, 0, 0, NULL, NULL, NULL, NULL },// This is the end marker
 };