Killing Transform Rep

Summary:
Let's get rid of TransformRep and it's children. We have confirmed that HashSkipListRep works better with multifeed, so there is no benefit to keeping this around.

This diff is mostly just deleting references to obsoleted functions. I also have a diff for fbcode that we'll need to push when we switch to new release.

I had to expose HashSkipListRepFactory in the client header files because db_impl.cc needs access to GetTransform() function for SanitizeOptions.

Test Plan: make check

Reviewers: dhruba, haobo, kailiu, sdong

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14397

db/db_impl.cc

@@ -50,6 +50,7 @@
 #include "util/auto_roll_logger.h"
 #include "util/build_version.h"
 #include "util/coding.h"
+#include "util/hash_skiplist_rep.h"
 #include "util/logging.h"
 #include "util/mutexlock.h"
 #include "util/perf_context_imp.h"
@@ -162,10 +163,10 @@ Options SanitizeOptions(const std::string& dbname,
     Log(result.info_log, "Compaction filter specified, ignore factory");
   }
   if (result.prefix_extractor) {
-    // If a prefix extractor has been supplied and a PrefixHashRepFactory is
+    // If a prefix extractor has been supplied and a HashSkipListRepFactory is
     // being used, make sure that the latter uses the former as its transform
     // function.
-    auto factory = dynamic_cast<PrefixHashRepFactory*>(
+    auto factory = dynamic_cast<HashSkipListRepFactory*>(
       result.memtable_factory.get());
     if (factory &&
         factory->GetTransform() != result.prefix_extractor) {