Add libint package (#1264)

* Add libint package

* Add Intel optimization flags recommended by CP2K

* Add new version and Intel compiler optimization flags for libxc

* Add older version of libint

* Libint depends on GMP C++ library

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

@@ -37,9 +37,12 @@ class Gmp(Package):
     version('6.0.0a', 'b7ff2d88cae7f8085bd5006096eed470')
     version('6.0.0',  '6ef5869ae735db9995619135bd856b84')
 
-    depends_on("m4", type='build')
+    depends_on('m4', type='build')
 
     def install(self, spec, prefix):
-        configure("--prefix=%s" % prefix)
+        configure('--prefix={0}'.format(prefix),
+                  '--enable-cxx')
+
         make()
-        make("install")
+        make('check')
+        make('install')