Fix broken build. Add stdint.h to get uint64_t

Summary:
I still get failures from this. Not sure whether there was a fix in progress.

Task ID: #

Blame Rev:

Test Plan:
compile

Revert Plan:

Database Impact:

Memcache Impact:

Other Notes:

EImportant:

- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -

Reviewers: dhruba

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D6147

include/leveldb/options.h

@@ -7,6 +7,7 @@
 
 #include <stddef.h>
 #include <string>
+#include <stdint.h>
 
 namespace leveldb {