Added all required dependencies

vendor/github.com/msteinert/pam/callback.go

@@ -0,0 +1,39 @@
+package pam
+
+import "sync"
+
+var cb struct {
+	sync.Mutex
+	m map[int]interface{}
+	c int
+}
+
+func init() {
+	cb.m = make(map[int]interface{})
+}
+
+func cbAdd(v interface{}) int {
+	cb.Lock()
+	defer cb.Unlock()
+	cb.c++
+	cb.m[cb.c] = v
+	return cb.c
+}
+
+func cbGet(c int) interface{} {
+	cb.Lock()
+	defer cb.Unlock()
+	if v, ok := cb.m[c]; ok {
+		return v
+	}
+	panic("Callback pointer not found")
+}
+
+func cbDelete(c int) {
+	cb.Lock()
+	defer cb.Unlock()
+	if _, ok := cb.m[c]; !ok {
+		panic("Callback pointer not found")
+	}
+	delete(cb.m, c)
+}