message: tests/unit/general/test_mem sysconf fix for AppVeyor
diff: // Software Foundation) version 2.1 dated February 1999.
  #include "mfem.hpp"
  -
  #include "catch.hpp"
  #ifndef _WIN32
  #include <unistd.h>
  #else
  -#define sysconf(...) 0x1000
  +#define sysconf(...) 0x10
  #endif
  using namespace mfem;
  