Spec.satisfies accesses Spec.concrete as property (#2928)

* Spec.satisfies accesses Spec.concrete as property

Fixes #2760

When copying a spec, _concrete is always set to False for each
dependency. "Spec.satisfies" was accessing the member "_concrete"
directly instead of using the property "concrete". This means that
if you copy a spec, the dependencies will be considered equal, but
did not necessarily satisfy one another. Spec.satisfies is a
prerequisite for a package to be considered an extension; as a
consequence, an extension with run-time dependencies that were also
extensions did not activate those extensions. This updates
Spec.satisfies to avoid checking the cached member "_concrete"
directly.

* Added test to check for activation of dependency extension

* Added test to check for transitive satisfiability between a spec and its copy

var/spack/repos/builtin.mock/packages/extendee/package.py

@@ -0,0 +1,39 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program 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) version 2.1, February 1999.
+#
+# This program 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 terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+from spack import *
+
+
+class Extendee(Package):
+    """A package with extensions"""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/extendee-1.0.tar.gz"
+
+    extendable = True
+
+    version('1.0', 'hash-extendee-1.0')
+
+    def install(self, spec, prefix):
+        pass

var/spack/repos/builtin.mock/packages/extension1/package.py

@@ -0,0 +1,39 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program 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) version 2.1, February 1999.
+#
+# This program 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 terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+from spack import *
+
+
+class Extension1(Package):
+    """A package which extends another package"""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/extension1-1.0.tar.gz"
+
+    extends('extendee')
+
+    version('1.0', 'hash-extension1-1.0')
+
+    def install(self, spec, prefix):
+        pass

var/spack/repos/builtin.mock/packages/extension2/package.py

@@ -0,0 +1,41 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program 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) version 2.1, February 1999.
+#
+# This program 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 terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+from spack import *
+
+
+class Extension2(Package):
+    """A package which extends another package. It also depends on another
+       package which extends the same package."""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/extension2-1.0.tar.gz"
+
+    extends('extendee')
+    depends_on('extension1', type=('build', 'run'))
+
+    version('1.0', 'hash-extension2-1.0')
+
+    def install(self, spec, prefix):
+        pass