This helps to avoid situations where 2 x unrelated AAF imports use the same name internally - and/or they give us meaningless session names like "Untitled.ardour"
This reverts commit b935710b60.
legalize_for_universal_path() already santizes the path in a way that is
safe for all OS.
laaf_util_clean_filename() cannot be used with .c_str() because the
function modifies the char* passed to it.
This worked in some cases before C++11, and can work with non-const
std::string::data starting at C++17, but C++11 spec is quite clear:
> The program shall not modify any of the values stored in the
> character array; otherwise, the behavior is undefined.
