feat: update stdlib mapping for go1.15

- drop stdlib for go1.13
- generate stdlib for go1.15
-  update CI configuration.

stdlib/go1_15_compress_zlib.go

@@ -0,0 +1,46 @@
+// Code generated by 'github.com/containous/yaegi/extract compress/zlib'. DO NOT EDIT.
+
+// +build go1.15,!go1.16
+
+package stdlib
+
+import (
+	"compress/zlib"
+	"go/constant"
+	"go/token"
+	"io"
+	"reflect"
+)
+
+func init() {
+	Symbols["compress/zlib"] = map[string]reflect.Value{
+		// function, constant and variable definitions
+		"BestCompression":    reflect.ValueOf(constant.MakeFromLiteral("9", token.INT, 0)),
+		"BestSpeed":          reflect.ValueOf(constant.MakeFromLiteral("1", token.INT, 0)),
+		"DefaultCompression": reflect.ValueOf(constant.MakeFromLiteral("-1", token.INT, 0)),
+		"ErrChecksum":        reflect.ValueOf(&zlib.ErrChecksum).Elem(),
+		"ErrDictionary":      reflect.ValueOf(&zlib.ErrDictionary).Elem(),
+		"ErrHeader":          reflect.ValueOf(&zlib.ErrHeader).Elem(),
+		"HuffmanOnly":        reflect.ValueOf(constant.MakeFromLiteral("-2", token.INT, 0)),
+		"NewReader":          reflect.ValueOf(zlib.NewReader),
+		"NewReaderDict":      reflect.ValueOf(zlib.NewReaderDict),
+		"NewWriter":          reflect.ValueOf(zlib.NewWriter),
+		"NewWriterLevel":     reflect.ValueOf(zlib.NewWriterLevel),
+		"NewWriterLevelDict": reflect.ValueOf(zlib.NewWriterLevelDict),
+		"NoCompression":      reflect.ValueOf(constant.MakeFromLiteral("0", token.INT, 0)),
+
+		// type definitions
+		"Resetter": reflect.ValueOf((*zlib.Resetter)(nil)),
+		"Writer":   reflect.ValueOf((*zlib.Writer)(nil)),
+
+		// interface wrapper definitions
+		"_Resetter": reflect.ValueOf((*_compress_zlib_Resetter)(nil)),
+	}
+}
+
+// _compress_zlib_Resetter is an interface wrapper for Resetter type
+type _compress_zlib_Resetter struct {
+	WReset func(r io.Reader, dict []byte) error
+}
+
+func (W _compress_zlib_Resetter) Reset(r io.Reader, dict []byte) error { return W.WReset(r, dict) }