petsc: add 64bit variant (#2655)

* petsc: add 64bit variant

* hypre: add int64 variant

* superlu-dist: add int64 variant

* petsc: add int64 variant

* metis: rename idx64 to int64 to make it consistent with other packages

* mumps: rename idx64 to int64 to make it consistent with other packages

* dealii: rename 64bit to int64 to make it consistent with other packages

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

@@ -55,7 +55,7 @@ class Mumps(Package):
             description='Activate the compilation of smumps')
     variant('complex', default=True,
             description='Activate the compilation of cmumps and/or zmumps')
-    variant('idx64', default=False,
+    variant('int64', default=False,
             description='Use int64_t/integer*8 as default index type')
     variant('shared', default=True, description='Build shared libraries')
 
@@ -125,7 +125,7 @@ def write_makefile_inc(self):
         fpic = '-fPIC' if '+shared' in self.spec else ''
         # TODO: test this part, it needs a full blas, scalapack and
         # partitionning environment with 64bit integers
-        if '+idx64' in self.spec:
+        if '+int64' in self.spec:
             makefile_conf.extend(
                 # the fortran compilation flags most probably are
                 # working only for intel and gnu compilers this is