[BUG] RetroWrite does not disassemble a set of functions

RetroWrite does not disassemble certain functions
especially when their symbol visibilities are 'STV_HIDDEN.'
Moreover, the omission causes recompilation errors.

I examined source code, and found the following code that filters out hidden functions.

https://github.com/HexHive/retrowrite/blob/120e73859c2d76b712bfd609ce91c0a8a4d003d7/librw_x64/loader.py#L202-L204

I think the above code should be removed to fix the bug.
Thank you.

Test Environment.
1. Platform: Ubuntu 18.04, x86-64
2. Compiler: gcc-7
3. Target binary: binutils-2.31.1/objcopy

Start in librw_x64/loader.py at the hidden-symbol filtering code linked in the issue, then reproduce the behavior with the binutils-2.31.1/objcopy target on Ubuntu 18.04 using gcc-7. Done means functions with STV_HIDDEN visibility are disassembled and the resulting output recompiles without errors.

Written by the indexing model from the issue text.