added neural networks benchmarks

As introduced by #1387 (closed). This PR adds the neural network benchmarks in a custom set. Also I am not sure how to give the include folder to goto-cc in the current pipeline. So I disabled the preprocessing check for the neural network benchmarks

• programs added to new and appropriately named directory

• license present and acceptable (in machine-readable comment at beginning of program as specified by the REUSE project)

• contributed-by present (either in README file or as comment at beginning of program)

• programs added to a .set file of an existing category, or new sub-category established (if justified)

• suggest to add it to benchmark definitions (.XML) in repositories for benchmark-definitions

• intended property matches the corresponding .prp file

• programs and expected answer added to a .yml file according to task definitions

• data model present in task-definition file
• original (ideally not preprocessed) sources present
• preprocessed files present
• preprocessed files generated with correct architecture
• Makefile added with correct content and without overly broad suppression of warnings