E_RECOVERABLE errors are reported as "Catchable fatal error". This is
misleading, because they actually can't be caught via try-catch statements.
Therefore we change the wording to "Recoverable fatal error" as suggested by
Nikita.
We currently don't show the argument at which the error actually
occured in the trace - should probably either add it or don't
display args on incomplete frames altogether, otherwise this'll
probably be confusing.