typo in ParseInteger
typo in ParseInteger

reported by Michael Stone.
Fixes issue 26.

R=r
CC=re2-dev
http://codereview.appspot.com/1844044

nelhage/re2,dragonkid/re2,nelhage/re2,nelhage/re2,dragonkid/re2,Distrotech/re2,tst2005googlecode/re2,pombreda/re2,dragonkid/re2,zeusdeux/re2,PiRSquared17/re2,tst2005googlecode/re2,zeusdeux/re2,lamuguo/re2,PiRSquared17/re2,Distrotech/re2,PiRSquared17/re2,tst2005googlecode/re2,Distrotech/re2,PiRSquared17/re2,tst2005googlecode/re2,nelhage/re2,pombreda/re2,lamuguo/re2,nelhage/re2,dragonkid/re2,nelhage/re2,PiRSquared17/re2,pombreda/re2,zeusdeux/re2,zeusdeux/re2,Distrotech/re2,dragonkid/re2,zeusdeux/re2,pombreda/re2,tst2005googlecode/re2,lamuguo/re2,pombreda/re2,Distrotech/re2,lamuguo/re2,lamuguo/re2