Remove legacy stuff in common.h (#20523)

* Remove old interop macro

* Remove legacy string macro things

* Unbreak the posix/linux/unix builds

* Add String::IEquals and use it for case insensitive compare

* Add missing include for posix

* Replace _strnicmp with String::StartsWith

* Add LoByte and HiByte into Util.h, swap macros

* Fix android build

* Hopefully last of the string things

* Replace STUB directly with the warning

src/openrct2/platform/Platform.Linux.cpp

@@ -14,6 +14,7 @@
 #    include <limits.h>
 #    include <locale.h>
 #    include <pwd.h>
+#    include <unistd.h>
 #    include <vector>
 #    if defined(__FreeBSD__) || defined(__NetBSD__)
 #        include <stddef.h>