MultiSource/Benchmarks/DOE-ProxyApps-C++/CLAMP: Fix build with newer libstdc++

[homerdin]

LGTM. Thanks for fixing this

MultiSource/Benchmarks/DOE-ProxyApps-C++/CLAMR/MallocPlus.h

struct malloc_plus_memory_entry {
    size_t  mem_ndims;     //!< number of dimensions
    size_t  mem_elsize;    //!< element size for type of data
    int     mem_flags;     //!< flags for special handling
    char   *mem_name;      //!< name of memory entry
 };
 
 struct cmp_str
 {
-   bool operator()(char const *a, char const *b)
+   bool operator()(const string &a, const string &b)
    {
-      return strcmp(a, b) < 0;
+      return a.compare(b) < 0;
    }
 };
 
 /****************************************************************//**
  * MallocPlus class
  *    Provide an enhanced memory allocation package with database
  *    of allocations, sizes and contiguous memory allocations for
  *    multi-dimensional arrays