Merge pull request #2992 from 9rnsr/fix6930

[enh] Issue 6930 - combined type of immutable(T) and inout(T) should be inout(const(T))
fix Issue 11755 - Operator <>= and !<>= with arrays make internal error in e2ir

Currently backend layer implicitly translates NCEG operators to the corresponding integer operators in non-floating comparisons. If no corresponding operator exists, it had been reported backend error, and now ICE causes.