leveldb: C: add Matt Proud (Google CLA).
leveldb: C: add Matt Proud (Google CLA).

LGTM=dsymonds
R=dsymonds
CC=golang-codereviews, matt.proud
https://codereview.appspot.com/148020044

mikewiacek/leveldb,scalingdata/leveldb-go,patterncat/leveldb-go,bryanxu/leveldb-go,eryx/leveldb-go,patterncat/leveldb-go,cxflag203/leveldb-go,golang/leveldb,iTalant/leveldb-go,oulan/leveldb-go,henderjon/leveldb-go,scalingdata/leveldb-go,bryanxu/leveldb-go,golang/leveldb,peterjliu/leveldb-go,shaunstanislaus/leveldb,peterjliu/leveldb-go,shaunstanislaus/leveldb,eryx/leveldb-go,cxflag203/leveldb-go,gaowenbin/leveldb,bonbizin/leveldb-go,oulan/leveldb-go,yh453926638/leveldb,henderjon/leveldb-go,iTalant/leveldb-go,mikewiacek/leveldb,bonbizin/leveldb-go,yh453926638/leveldb,shadowpriest/leveldb-go,gaowenbin/leveldb,shadowpriest/leveldb-go