[ opt ] Made all fields of state strict.
Revert "[ opt ] Made all fields of state strict."

This reverts commit f63c349610da2ff79dc3b534147434a42f20fcbd.

Effect on library-test was 2-3 sec more (3 min 16 instead of 3 min 14
user time (Andreas' laptop)).
[ clarify ] Compute Range of AmbiguousQName from the first QName.
[ Highlighting ] Collect constructor disambiguation during type checking.
[ Highlighting ] Use stored constructor disambiguation...

... instead of traversing internal syntax.
Simplified the code quite a bit.
library-test time allocated for highlighting down from 6 to 1
sec (Andreas laptop).
Overall time not significantly reduced.
[ bench ] library-test (Andreas' laptop).
[ Highlighting ] Updated interaction output.
Merge /home/abel/agda into maint-2.4.2