Summary:
util/testutil.h doesn't seem to be used in tools/sst_dump_tool_imp.h. Remove it.
Also move some other include to tools/sst_dump_tool.cc instead.
Test Plan: Build with GCC, CLANG and with GCC 4.81 and 4.9.
Reviewers: yuslepukhin, yhchiang, rven, anthony, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D52791