Define our own constants for all supported MDB C errors.
Define our own constants for all supported MDB C errors.

You might be tempted to use others at times, but they'll break mdb_strerror and thus db_strerror on Windows.
It might be a good idea to write our own db_strerror from scratch so we can support other errors as well.

Lacra17/stronglink,btrask/stronglink,feld/stronglink,yamingd/stronglink,btrask/stronglink,rmoorman/stronglink,Ryezhang/stronglink,iOSCowboy/stronglink,btrask/stronglink,guiquanz/stronglink,shaunstanislaus/stronglink,guiquanz/stronglink,iOSCowboy/stronglink,Lacra17/stronglink,shaunstanislaus/stronglink,btrask/stronglink,nkatsaros/stronglink,feld/stronglink,rmoorman/stronglink,nkatsaros/stronglink,nkatsaros/stronglink,shaunstanislaus/stronglink,feld/stronglink,yamingd/stronglink,Ryezhang/stronglink,rmoorman/stronglink,yamingd/stronglink,guiquanz/stronglink,Lacra17/stronglink,iOSCowboy/stronglink,Ryezhang/stronglink