[cs/java] clean output directory of old files
Merge pull request #3613 from nadako/clean_out_dir

[cs/java] clean output directory of old files
[cs] don't try to clean output directory when -D unity-std-target for now
[cpp] Add WeakMap implementation
Merge branch 'development' of https://github.com/HaxeFoundation/haxe into development
[display] add @type mode
Merge pull request #3622 from nadako/display-type

[display] add @type mode
add --each to advanced argument specification (closes #3624)
Typo fix
Merge pull request #3627 from Gama11/patch-10

Typo fix
fix static call through abstract instance check (see #3616)
submodule update
increase functional nerdiness
add a function to get type error text
add a test for #3616
revert because haxelib
- change interface of `type_generic_function` to deal with overriding (closes #3592)
- also make inline actually work
respect abstract paths in `patch_class` (see #3500)
add EqDoNotFollowNull and `can_follow` to `type_eq`
do not consider `Null<T>` and `T` equal when determining if an inlined expression requires a cast (see #3585)