fix Issue 3449 - const and invariant struct members do not behave according to spec
refactor - reduce CTFE memory consumption pt 1
add target for default dmd.conf

- works for the common dmd/druntime/phobos folder layout

- does not overwrite existing dmd.conf files
use std.algorithm: cmp
better error message when the same file is specified twice on the command line
Merge pull request #4122 from 9il/cmp

use std.algorithm: cmp
Merge pull request #4098 from MartinNowak/dmdConf

add target for default dmd.conf
Merge pull request #4123 from rainers/issue13704

Fix issue 13704 - Confusing error message when passing the same on the command line twice
Merge pull request #4042 from 9rnsr/fix3449

Issue 3449 - const and invariant struct members do not behave according to spec
Fix Issue 13707 - msvc32 C++ struct return ABI not followed for structs with constructors

A constructor should stop a struct from being passed in registers on win32/C++.
Change traits table back to using a sentinel value
Merge pull request #4124 from yebblies/issue13707

[DDMD] Issue 13707 - msvc32 C++ struct return ABI not followed for structs with constructors
Merge pull request #4125 from yebblies/traitstable

[DDMD] Change traits table back to using a sentinel value
Merge pull request #4114 from WalterBright/ctfe-1

refactor - reduce CTFE memory consumption pt 1