Encoding fixer update - no detecting problems, remove BOM from file

Due to idea of focusing on fixing errors, not detecting them - 1 of 3 PR that update project to not detecting issues.
@fabpot, what if file is in other encoding like UTF-1 or SCSU (which have a differ BOM mark), and that file do not has it's ow BOM mark, but has UTF-8 BOM as content (not as BOM)? It can be even file in encoding which do not support BOM mark, and still has a UTF8BOM mark as content.
I agree it is a extremely rare case, but it could happen - and if it is rare case we could ignore it and then not need to lose time on detecting encoding and need a mbstring ext. What do you think?