fix dealii dependencies for Clang 9.1.0 C++17 (#7644)

* fix boost and muparser for Clang 9.1.0 with C++17

* muparser: add C++11 flags

* dealii: temporary disable python by default

* dealii: make CMake find right python

var/spack/repos/builtin/packages/boost/array_binary_tree.patch

@@ -0,0 +1,12 @@
+diff --git a/boost/graph/detail/array_binary_tree.hpp b/boost/graph/detail/array_binary_tree.hpp
+index e59da9e..fd403d1 100644
+--- a/boost/graph/detail/array_binary_tree.hpp
++++ b/boost/graph/detail/array_binary_tree.hpp
+@@ -14,6 +14,7 @@
+ #include <iterator>
+ #include <functional>
+ #include <boost/config.hpp>
++#include <boost/iterator.hpp>
+ 
+ namespace boost {
+ 

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

@@ -46,8 +46,10 @@ class Boost(Package):
             branch='develop',
             submodules=True)
 
+    version('1.67.0.b1', '3423a4a3ec5297051fd27091864630e2dce4c159',
+            url='https://dl.bintray.com/boostorg/beta/1.67.0.beta.1/source/boost_1_67_0_b1.tar.gz')
     version('1.66.0', 'b6b284acde2ad7ed49b44e856955d7b1ea4e9459',
-            url='https://dl.bintray.com/boostorg/release/1.66.0/source/boost_1_66_0.tar.bz2')
+            url='https://dl.bintray.com/boostorg/release/1.66.0/source/boost_1_66_0.tar.bz2', preferred=True)
     version('1.65.1', '41d7542ce40e171f3f7982aff008ff0d',
             url='https://dl.bintray.com/boostorg/release/1.65.1/source/boost_1_65_1.tar.bz2')
     version('1.65.0', '5512d3809801b0a1b9dd58447b70915d',
@@ -151,6 +153,9 @@ class Boost(Package):
 
     conflicts('+taggedlayout', when='+versionedlayout')
 
+    # temporary fix https://svn.boost.org/trac10/ticket/13505
+    patch('array_binary_tree.patch', when='@1.67.0.b1')
+
     # Patch fix from https://svn.boost.org/trac/boost/ticket/11856
     patch('boost_11856.patch', when='@1.60.0%gcc@4.4.7')