RAR5 reader: fix ARM filter going beyond window buffer boundary

RAR5 reader: fix ARM filter going beyond window buffer boundary

RAR5 uses filters in order to mutate data just before compression, to
achieve a better compression ratio. After decompression, this mutation
needs to be reversed by processing various filters that the compressor
uses.

One of such filters is an ARM executable file filter, which changes some
bytes in the input stream if the stream is recognized as an executable
file with ARM native code.

This commit fixes the situation when the decompressor using an ARM filter
was referencing a byte outside current window buffer. Such action is
invalid and can produce segmentation faults.

This commit also adds a test using OSSFuzz sample #15431.