Add new package: byacc (#16123)

* Add new package: byacc

* refine byacc info

var/spack/repos/builtin/packages/byacc/package.py

@@ -0,0 +1,24 @@
+# Copyright 2013-2020 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+from spack import *
+
+
+class Byacc(AutotoolsPackage):
+    """Berkeley Yacc is an LALR(1) parser generator.  Berkeley Yacc has
+    been made as compatible as possible with AT&T Yacc.  Berkeley Yacc
+    can accept any input specification that conforms to the AT&T Yacc
+    documentation. Specifications that take advantage of undocumented
+    features of AT&T Yacc will probably be rejected."""
+
+    homepage = "https://github.com/grandseiken/byacc"
+    git      = "https://github.com/grandseiken/byacc.git"
+
+    version('master', branch='master')
+
+    depends_on('m4',       type='build')
+    depends_on('autoconf', type='build')
+    depends_on('automake', type='build')
+    depends_on('libtool',  type='build')