Workaround clang error introduced by 3117036b80

:
"template argument for non-type template parameter is treated as function type 'bool (bool)'"

Eigen/src/Core/util/StaticAssert.h

@@ -107,9 +107,9 @@
         {Eigen::internal::static_assertion<bool(CONDITION)>::MSG;}
 
     #else
-
+      // In some cases clang interprets bool(CONDITION) as function declaration
       #define EIGEN_STATIC_ASSERT(CONDITION,MSG) \
-        if (Eigen::internal::static_assertion<bool(CONDITION)>::MSG) {}
+        if (Eigen::internal::static_assertion<static_cast<bool>(CONDITION)>::MSG) {}
 
     #endif