feat: update stdlib mapping for go1.15

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

stdlib/go1_15_text_scanner.go

@@ -0,0 +1,41 @@
+// Code generated by 'github.com/containous/yaegi/extract text/scanner'. DO NOT EDIT.
+
+// +build go1.15,!go1.16
+
+package stdlib
+
+import (
+	"go/constant"
+	"go/token"
+	"reflect"
+	"text/scanner"
+)
+
+func init() {
+	Symbols["text/scanner"] = map[string]reflect.Value{
+		// function, constant and variable definitions
+		"Char":           reflect.ValueOf(constant.MakeFromLiteral("-5", token.INT, 0)),
+		"Comment":        reflect.ValueOf(constant.MakeFromLiteral("-8", token.INT, 0)),
+		"EOF":            reflect.ValueOf(constant.MakeFromLiteral("-1", token.INT, 0)),
+		"Float":          reflect.ValueOf(constant.MakeFromLiteral("-4", token.INT, 0)),
+		"GoTokens":       reflect.ValueOf(constant.MakeFromLiteral("1012", token.INT, 0)),
+		"GoWhitespace":   reflect.ValueOf(constant.MakeFromLiteral("4294977024", token.INT, 0)),
+		"Ident":          reflect.ValueOf(constant.MakeFromLiteral("-2", token.INT, 0)),
+		"Int":            reflect.ValueOf(constant.MakeFromLiteral("-3", token.INT, 0)),
+		"RawString":      reflect.ValueOf(constant.MakeFromLiteral("-7", token.INT, 0)),
+		"ScanChars":      reflect.ValueOf(constant.MakeFromLiteral("32", token.INT, 0)),
+		"ScanComments":   reflect.ValueOf(constant.MakeFromLiteral("256", token.INT, 0)),
+		"ScanFloats":     reflect.ValueOf(constant.MakeFromLiteral("16", token.INT, 0)),
+		"ScanIdents":     reflect.ValueOf(constant.MakeFromLiteral("4", token.INT, 0)),
+		"ScanInts":       reflect.ValueOf(constant.MakeFromLiteral("8", token.INT, 0)),
+		"ScanRawStrings": reflect.ValueOf(constant.MakeFromLiteral("128", token.INT, 0)),
+		"ScanStrings":    reflect.ValueOf(constant.MakeFromLiteral("64", token.INT, 0)),
+		"SkipComments":   reflect.ValueOf(constant.MakeFromLiteral("512", token.INT, 0)),
+		"String":         reflect.ValueOf(constant.MakeFromLiteral("-6", token.INT, 0)),
+		"TokenString":    reflect.ValueOf(scanner.TokenString),
+
+		// type definitions
+		"Position": reflect.ValueOf((*scanner.Position)(nil)),
+		"Scanner":  reflect.ValueOf((*scanner.Scanner)(nil)),
+	}
+}