fix Issue 11919 - GitHub HEAD regression for getAttributes trait (DMD CORE DUMP)

fix insufficient error propagation in TupleExp::semantic to resolve ICE.
fix Issue 9741 - undefined identifier with User Defined Attribute

Also fixes incorrect 'undefined identifier' error in `fail_compilation/ice11919.d`.
fix Issue 11914 - Missed tuple unpacking in foreach for cartesianProduct
Merge pull request #3090 from 9rnsr/fix11919

[REG2.066a] Issue 11919 - GitHub HEAD regression for getAttributes trait (DMD CORE DUMP)
Merge pull request #3091 from 9rnsr/fix11914

[REG2.065a] Issue 11914 - Missed tuple unpacking in foreach for cartesianProduct
fix Issue 11926 - Segmentation fault when using const in an enum
fix Issue 11925 - ICE in CompoundStatement::semantic
Merge pull request #3099 from 9rnsr/fix11925

[REG2.065a] Issue 11925 - ICE in CompoundStatement::semantic
Merge pull request #3098 from 9rnsr/fix11926

Issue 11926 - Segmentation fault when using const in an enum
Clean up some comments that don't convert easily
Remove dead predefined version code
Merge pull request #3102 from yebblies/D_Bits

[trivial] Remove dead predefined version code
Merge pull request #3101 from yebblies/comments1

[DDMD] Clean up some comments that don't convert easily