Automatically validate patch after evaluating them

[musjj]

It would be nice if patches would get automatically validated right after its definition is evaluated. This would eliminate the need of remembering to manually validate them every once in a while.

[raxod502]

You wouldn't want to do this during startup due to the heavy performance implications, but since el-patch is (due to #11) entirely computable at compile-time, I would not be opposed to adding an option for this to be done automatically in the case that patches are being compiled.