Support of DOL and REL file formats (Gamecube Wii)

Email from one of our users:

_Following up on our twitter exchange I will provide you with some sample files. I would like the ReDec IDA plugin to work on the dol and rel file formats, both of which can be found on Nintendo consoles from Gamecube-Wii U. The processor is PowerPC Big Endian. Dol is simply a stripped elf file while rel is designed to function like a dynamic link library (DLL). The body is almost identical to that of the elf and dol file format and just features a new header with a custom entry function. Full documentation for those formats exists and more importantly, there is also a loader plugin for IDA available here: https://github.com/heinermann/ida-wii-loaders/releases_

_Both file formats can be easily opened with those and the structure is fully parsed near identical to that of any elf file. Furthermore cutting out a raw function and decompiling it using the ReDec web interface does work fine, but I would prefer to work in IDA to take advantage of the additional convenience and already figured out function names and arguments. See the attached zip file for small samples of both formats that can be opened in IDA with the provided loader. I also included the disassembly export from IDA._

[dol_rel.zip](https://github.com/avast-tl/retdec-idaplugin/files/1674328/dol_rel.zip)

Maybe, we could solve this by using raw decompilation. If not, these formats would have to be supported by RetDec's fileformat library. Explore and decide.