[GM Commands] Split GM Commands Into Separate Files (#1766)

* Split GM commands into their own files

* Code cleanup

zone/gm_commands/lastname.cpp

@@ -0,0 +1,19 @@
+#include "../client.h"
+
+void command_lastname(Client *c, const Seperator *sep)
+{
+	Client *t = c;
+
+	if (c->GetTarget() && c->GetTarget()->IsClient()) {
+		t = c->GetTarget()->CastToClient();
+	}
+	LogInfo("#lastname request from [{}] for [{}]", c->GetName(), t->GetName());
+
+	if (strlen(sep->arg[1]) <= 70) {
+		t->ChangeLastName(sep->arg[1]);
+	}
+	else {
+		c->Message(Chat::White, "Usage: #lastname <lastname> where <lastname> is less than 70 chars long");
+	}
+}
+