cmd/evm, core/asm: add EVM assembler (#3686)

The evm compile command implements a simple assembly language that compiles to
EVM bytecode.

core/asm/lex_test.go

@@ -0,0 +1,36 @@
+// Copyright 2017 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/>.
+
+package asm
+
+import "testing"
+
+func lexAll(src string) []token {
+	ch := Lex("test.asm", []byte(src), false)
+
+	var tokens []token
+	for i := range ch {
+		tokens = append(tokens, i)
+	}
+	return tokens
+}
+
+func TestComment(t *testing.T) {
+	tokens := lexAll(";; this is a comment")
+	if len(tokens) != 2 { // {new line, EOF}
+		t.Error("expected no tokens")
+	}
+}