ResultHandler->getFieldNumber optimization
ResultHandler->getFieldNumber optimization

I've profiled an application with a SQL query that returns tons of fields, and Blackfire flagged the `ResultHandler->getFieldNumber` as a performance bottleneck.
It was called 12 078 times, and 98% of the time spent on method was due to a call on `sprintf`.
Doing a concatenation instead solved that specific bottleneck.

Here's the profiler graph:

![profiler graph](https://i.imgur.com/zHUHKZX.png).

Do you think the change is worth it?
pomm-project/Foundation,stood/Foundation