Update logging.cc

fix cast style to cpp static_cast
Update logging.cc
remove cast, replace %llu with % PRIu64
Merge pull request #306 from Liuchang0812/fix_cast

Update logging.cc
dont create backup_input if compaction filter v2 is not used

Summary:
Compaction creates backup_input iterator even though it only needed
when compaction filter v2 is enabled

Test Plan: make all check

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23769
change target_file_size_base to uint64_t

Summary: It contrains the file size to be 4G max with int

Test Plan:
tried to grep instance and made sure other related variables are also
uint64

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23697