add deadlock mutex package

write to deadlock stderr after closing gocui

more deadlock checking

vendor/github.com/petermattis/goid/runtime_gccgo_go1.8.go

@@ -0,0 +1,16 @@
+// +build gccgo,go1.8
+
+package goid
+
+// https://github.com/gcc-mirror/gcc/blob/gcc-7-branch/libgo/go/runtime/runtime2.go#L329-L422
+
+type g struct {
+	_panic       uintptr
+	_defer       uintptr
+	m            uintptr
+	syscallsp    uintptr
+	syscallpc    uintptr
+	param        uintptr
+	atomicstatus uint32
+	goid         int64 // Here it is!
+}