Remove backconfig in favor of using DMD's copy

Author: Geod24

README.md

@@ -14,9 +14,37 @@ https://digitalmars.com/ctg/sc.html
    `shared stdout = &_iob[1];`
    with
    `enum stdout = &_iob[1];`.
-4. Change directory to `dm\src\dmc`
-5. Make sure the `dm\bin\make.exe` program is on your `PATH`.
-6. Execute the commands:
+4. Run `git submodule update --init` to make sure you have up-to-date submodules.
+5. Change directory to `dm\src\dmc`
+6. Make sure the `dm\bin\make.exe` program is on your `PATH`.
+7. Execute the commands:
    `make clean`
    `make scppn`
 You might need to edit the `makefile` to set the path to your DMD installation.
+
+# Updating the backend
+
+In order to update the backend to a more recent version, do the following:
+1. Go to the DMD submodule:  `cd dm/src/dmd`;
+2. Fetch the latest commits: `git fetch`
+3. Checkout the desired commit, e.g.:
+   - `git checkout origin/master`: Checkout the latest version of the DMD backend;
+   - `git checkout v2.095.0`: Checkout the state of the backend as of DMD v2.095.0;
+   - `git checkout 385312b93`: Checkout the state of the backend as of commit `385312b93`;
+4. Leave the `dmd` repository, e.g. `cd ../../` to come back to the root of this repository;
+5. Commit the change to the submodule: `git add dm/src/dmd && git commit -m "Update DMD backend to master"`
+
+Alternatively, when pulling from this repository, remember to always run `git submodule update --init`
+if the submodule have been updated. This is visible from `git status`:
+```shell
+$ git diff
+diff --git a/dm/src/dmd b/dm/src/dmd
+index 123456789..abcdef123 160000
+--- a/dm/src/dmd
++++ b/dm/src/dmd
+@@ -1 +1 @@
+-Subproject commit 67ca0a14c4d4d3161541eda27a4126f889d53546
++Subproject commit 385312b93239311c038ffd8c221ac62738006382
+```
+
+To learn more about `git submodule`, see [this section of the Pro Git book](https://git-scm.com/book/en/v2/Git-Tools-Submodules).