Rewrite ORMTable::unprefixFieldNames

This method is called a lot (~1000 times each time). It calls
the callback function ~10 times per table, resulting in ~10000
calls of strlen. Which is just not necesarry. The string length does
not change.

Change-Id: I19194f1166da465a1c9ef4b2fb9cdaef4105a6f7
Merge "Rewrite ORMTable::unprefixFieldNames"