Eliminate use of __attribute__

Ideally this would be standard C++, but here I've settled for things that should be supported by both clang and VS/cl.exe:
- Deprecated attribute retained, but now uses __declspec syntax
- Packed attribute replaced with pragma pack, except one instance where it unnecessary
- Aligned attribute replaced with explicit padding bytes inserted in the structs where needed
- Unused attribute simply removed (though where possible, the unused entities were also removed)

osx/boe.fileio.h

@@ -47,7 +47,7 @@ bool load_scenario_header(fs::path filename/*,short header_entry*/);
 //short get_buf_ptr(short flag);
 //bool check_p (short pword);
 
-void init_town() __attribute__((deprecated));
+__declspec(deprecated) void init_town();
 
 //void port_talk_nodes();
 //void port_town();