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 11885 - ICE(s2ir.c 359) with continuing a labeled ByLine (range struct w/ dtor) loop
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
Merge branch 'master' into rmdup
Merge pull request #3451 from WalterBright/rmdup

excise .dup and .idup from compiler
Merge pull request #3449 from 9rnsr/fix7887

Issue 7887 - [CTFE] can't assign to returned reference
Merge pull request #3375 from Trass3r/optref

do dead code elimination in release with debug info mode