Uses std::transform to allow compiler to find transform.

Will not send upstream.

--- IlmImf/ImfDwaCompressor.cpp	2016-11-17 13:58:52.789434004 +0000

+++ IlmImf/ImfDwaCompressor.cpp	2016-11-17 13:59:23.065747841 +0000

@@ -255,7 +255,7 @@

         _caseInsensitive(caseInsensitive)

     {

         if (caseInsensitive) 

-            transform(_suffix.begin(), _suffix.end(), _suffix.begin(), tolower);

+            std::transform(_suffix.begin(), _suffix.end(), _suffix.begin(), tolower);

     }

     Classifier (const char *&ptr, int size)

@@ -304,7 +304,7 @@

         if (_caseInsensitive) 

         {

             std::string tmp(suffix);

-            transform(tmp.begin(), tmp.end(), tmp.begin(), tolower);

+            std::transform(tmp.begin(), tmp.end(), tmp.begin(), tolower);

             return tmp == _suffix;

         }