Global code ovehaul - remove CAS and other, add 15 minute greet check

- Remove CAS, as it no longer works for us
- Remove other checks
- Implement 15 minute greet timeout check
- Fix chat logos
- Ditch thirdparty logger, use stdlib log facility wrapper for logging

internal/elog/types.go

@@ -0,0 +1,21 @@
+package elog
+
+import (
+	"sync"
+	"time"
+)
+
+// chatLock serialises writes for one chat so that two goroutines cannot splice
+// their lines into the same file.
+type chatLock struct {
+	mu sync.Mutex
+
+	// refs counts goroutines holding or waiting for this entry. It is only
+	// ever read or written while registryMu is held, which is what makes it a
+	// usable proof of "nobody is holding this" during eviction.
+	refs int
+
+	lastUsed time.Time
+}
+
+/* vim: set ft=go noet ai ts=4 sw=4 sts=4: */