New packages: libmo-unpack and py-mo-pack (#11895)

* libmo-unpack: package to encode and decode UM fields
* py-mo-pack: python interface for libmo-unpack

var/spack/repos/builtin/packages/libmo-unpack/package.py

@@ -0,0 +1,18 @@
+# Copyright 2013-2019 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 LibmoUnpack(CMakePackage):
+    """A library for handling the WGDOS and RLE compression schemes
+    used in UM files."""
+
+    homepage = "https://github.com/SciTools/libmo_unpack"
+    url      = "https://github.com/SciTools/libmo_unpack/archive/v3.1.2.tar.gz"
+
+    version('3.1.2', sha256='e09ef3e6f1075144acc5d6466b4ef70b2fe32ed4ab1840dd4fb7e15a40f3d370')
+
+    depends_on('check')

var/spack/repos/builtin/packages/py-mo-pack/package.py

@@ -0,0 +1,20 @@
+# Copyright 2013-2019 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 PyMoPack(PythonPackage):
+    """Packing methods used to encode and decode the data payloads of
+    Met Office Unified Model 'fields'"""
+
+    homepage = "https://github.com/SciTools/mo_pack"
+    url      = "https://github.com/SciTools/mo_pack/archive/v0.2.0.tar.gz"
+
+    version('0.2.0', sha256='4aa70e1f846b666670843bc2514435dedf7393203e88abaf74d48f8f2717a726')
+
+    depends_on('libmo-unpack')
+    depends_on('py-numpy', type=('build', 'run'))
+    depends_on('py-cython', type=('build', 'run'))