Fixing warnings generated by clang 8.0 on Windows

* Deprecation removals previously specific to MSVC/Intel now also used
  by clang
* String literals were assigned to non const pointers. These are stored
  in mutable arrays now
* An implicit function pointer to pointer conversion is a Microsoft
  extension warning is suppressed by an explicit reinterpret_cast
* The MSVC specific deprecation macro for jsoncpp was moved after the
  clang macro to avoid redefinition warnings. This is consistent with
  how jsoncpp fixed the issue in 36d8cfd7