Fixes#1284
Appearently, there is a use-case of stringifying the error in order to
evaluated its properties on another system. There was a regression
from 4.0.5 to 4.0.6 that the column-property of compilation errors
was not enumerable anymore in 4.0.6 (due to commit 20c965c) and
thus was not included in the output of "JSON.stringify".
Nils Knappmeier
a023cb4dd9