Proper hash function for std pairs
Proper hash function for std pairs

Change-Id: I817bd1cff4eb513f2c444a7180f78d89bd9889f6

mylxiaoyi/TheiaSfM,zhanshenman/TheiaSfM,zhanshenman/TheiaSfM,klemmster/TheiaSfM,mylxiaoyi/TheiaSfM,zhanshenman/TheiaSfM,klemmster/TheiaSfM,klemmster/TheiaSfM,mylxiaoyi/TheiaSfM,klemmster/TheiaSfM,zhanshenman/TheiaSfM,rajvishah/TheiaSfM,klemmster/TheiaSfM,mylxiaoyi/TheiaSfM,zhanshenman/TheiaSfM,rajvishah/TheiaSfM,rajvishah/TheiaSfM,whuaegeanse/TheiaSfM,whuaegeanse/TheiaSfM,whuaegeanse/TheiaSfM,rajvishah/TheiaSfM,whuaegeanse/TheiaSfM,mylxiaoyi/TheiaSfM