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;
         }