remove old compress workaround needed for pre Go 1.7

common/block.go

@@ -276,9 +276,9 @@ func NewDecodedBlock(data []byte, colors *Colors) (db *DecodedBlock, err error)
 
 	// There is a bug before Go 1.7 that enforces
 	// to add 4 as an offset after the compressed
-	// geometry data. This is resolved via build tags
-	// and definitions in pre17offset.go and
-	// post17offset.go.
+	// geometry data. As we now require at least 1.20
+	// this is no longer an issue.
+	const afterCompressOfs = 0
 	offset += buf.Pos + afterCompressOfs
 	buf.Pos = 0
 	if offset >= dataLen {

common/post17offset.go

@@ -1,10 +0,0 @@
-// Copyright 2016 by Sascha L. Teichmann
-// Use of this source code is governed by the MIT license
-// that can be found in the LICENSE file.
-
-// +build go1.7
-
-package common
-
-// afterCompressOfs is not necessary after Go 1.7.
-const afterCompressOfs = 0

common/pre17offset.go

@@ -1,10 +0,0 @@
-// Copyright 2016 by Sascha L. Teichmann
-// Use of this source code is governed by the MIT license
-// that can be found in the LICENSE file.
-
-// +build !go1.7
-
-package common
-
-// afterCompressOfs is necessary before Go 1.7.
-const afterCompressOfs = 4