feat: update stdlib mapping for go1.16

- drop stdlib for go1.14
- generate stdlib for go1.16
-  update CI configuration.

stdlib/go1_16_sync.go

@@ -0,0 +1,39 @@
+// Code generated by 'yaegi extract sync'. DO NOT EDIT.
+
+// +build go1.16
+
+package stdlib
+
+import (
+	"reflect"
+	"sync"
+)
+
+func init() {
+	Symbols["sync"] = map[string]reflect.Value{
+		// function, constant and variable definitions
+		"NewCond": reflect.ValueOf(sync.NewCond),
+
+		// type definitions
+		"Cond":      reflect.ValueOf((*sync.Cond)(nil)),
+		"Locker":    reflect.ValueOf((*sync.Locker)(nil)),
+		"Map":       reflect.ValueOf((*sync.Map)(nil)),
+		"Mutex":     reflect.ValueOf((*sync.Mutex)(nil)),
+		"Once":      reflect.ValueOf((*sync.Once)(nil)),
+		"Pool":      reflect.ValueOf((*sync.Pool)(nil)),
+		"RWMutex":   reflect.ValueOf((*sync.RWMutex)(nil)),
+		"WaitGroup": reflect.ValueOf((*sync.WaitGroup)(nil)),
+
+		// interface wrapper definitions
+		"_Locker": reflect.ValueOf((*_sync_Locker)(nil)),
+	}
+}
+
+// _sync_Locker is an interface wrapper for Locker type
+type _sync_Locker struct {
+	WLock   func()
+	WUnlock func()
+}
+
+func (W _sync_Locker) Lock()   { W.WLock() }
+func (W _sync_Locker) Unlock() { W.WUnlock() }