vendor: add github.com/Azure/go-ansiterm for --progress on Windows support

vendor/github.com/Azure/go-ansiterm/osc_string_state.go

@@ -0,0 +1,31 @@
+package ansiterm
+
+type oscStringState struct {
+	baseState
+}
+
+func (oscState oscStringState) Handle(b byte) (s state, e error) {
+	oscState.parser.logf("OscString::Handle %#x", b)
+	nextState, err := oscState.baseState.Handle(b)
+	if nextState != nil || err != nil {
+		return nextState, err
+	}
+
+	switch {
+	case isOscStringTerminator(b):
+		return oscState.parser.ground, nil
+	}
+
+	return oscState, nil
+}
+
+// See below for OSC string terminators for linux
+// http://man7.org/linux/man-pages/man4/console_codes.4.html
+func isOscStringTerminator(b byte) bool {
+
+	if b == ANSI_BEL || b == 0x5C {
+		return true
+	}
+
+	return false
+}