do dead code elimination in release with debug info mode
fix Issue 12009 - local import and "unable to resolve forward reference" error

`Module::semantic2` could be invoked from local imports, even when some
local symbol semantics are not yet completed.
fix Issue 11906 - Compiler assertion when comparing function pointers

If `f->isImportedSymbol()` is true, the translation from `AddrExp(VarExp(f))` to `SymOffExp(f)` in `AddrExp::optimize` will be skipped.
Therefore, the assertion is just wrong.
Merge pull request #3445 from 9rnsr/fix11906

Issue 11906 - Compiler assertion when comparing function pointers
fix Issue 11885 - ICE(s2ir.c 359) with continuing a labeled ByLine (range struct w/ dtor) loop
fix Issue 12179 - [ICE](e2ir.c 1861) with array operation
Merge pull request #3427 from 9rnsr/fix12179

[REG2.065] Issue 12179 - [ICE](e2ir.c 1861) with array operation
fix Issue 10169 - duplicate error message: member is not accessible
Merge pull request #3446 from 9rnsr/fix11885

Issue 11885 - ICE(s2ir.c 359) with continuing a labeled ByLine (range struct w/ dtor) loop
Merge pull request #3418 from 9rnsr/fix12009

Issue 12009 - local import and "unable to resolve forward reference" error
fix Issue 12508 - Codegen bug for interface type covariant return with lambda type inference
Merge pull request #3448 from 9rnsr/fix10169

Issue 10169 - duplicate error message: member is not accessible
Add -boundscheck=[on|safeonly|off] option

Replaces -noboundscheck (which becomes deprecated)

Fixes issue #12550
Merge pull request #3417 from 9rnsr/fix12508

Issue 12508 - Codegen bug for interface type covariant return with lambda type inference
fix Issue 7887 - [CTFE] can't assign to returned reference
Change the diagnostic for wrongly imported modules to explicitly state how to import the target module.
Cleanup -vgc implementation
Merge pull request #3405 from jpf91/cleanVGC

Cleanup -vgc implementation
Merge pull request #3443 from eco/boundscheck

Add -boundscheck=[on|safeonly|off] option
excise .dup and .idup from compiler