Updated shared_ptr header to allow it to be used with clang on linux independent of runtime library

include/crossplatform_shared_ptr.h

@@ -6,8 +6,16 @@
 // Based on the platform and compiler, include the necessary header to give access to std::tr1::shared_ptr directly as shared_ptr
 
 #if defined(__ISLINUX__) && (defined(__llvm__) || defined(__clang__)) // CLANG
-    #include <memory>
-    using std::shared_ptr;
+	#if __has_include(<tr1/memory>)
+        // CLANG and -stdlib=libstdc++
+        // See also http://stackoverflow.com/questions/13445742/apple-and-shared-ptr
+        #include <tr1/memory>
+        using namespace std::tr1;
+    #else
+        // CLANG and -stdlib=libc++
+        #include <memory>
+        using std::shared_ptr;
+    #endif
 #elif defined(__ISLINUX__) // GCC
     #include <tr1/memory>
     using namespace std::tr1;