mobile: remove support for Go < 1.7

mobile/big.go

@@ -93,3 +93,8 @@ func (bi *BigInts) Set(index int, bigint *BigInt) error {
 	bi.bigints[index] = bigint.bigint
 	return nil
 }
+
+// GetString returns the value of x as a formatted string in some number base.
+func (bi *BigInt) GetString(base int) string {
+	return bi.bigint.Text(base)
+}

mobile/big_go1.7.go

@@ -1,26 +0,0 @@
-// Copyright 2016 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-// Contains the wrappers from the math/big package that require Go 1.7 and above.
-
-// +build go1.7
-
-package geth
-
-// GetString returns the value of x as a formatted string in some number base.
-func (bi *BigInt) GetString(base int) string {
-	return bi.bigint.Text(base)
-}