radisk: md5 hash file names > 255 characters

[nsreed]

This solves the issue of radisk attempting to write to filenames with lengths exceeding the 255 character limit of most filesystems (issue here: #1070).

This is a different approach than that used in #1005 and touches only the ename function. If the sanitized file name would exceed the limit set by opt.maxKeyLength (and maxKeyLength is greater than 32 bytes required for the hash), I return an MD5 hash instead. The modification should also leave the browser radisk functionality untouched, to avoid compatibility issues. If this is a bad approach, or I haven't fully understood how ename works, my apologies.

I do not know whether it is necessary to add the hashes to the %1C file, since the path hashes are deterministic. If this is necessary, I need guidance on how to interact with that file. I have created a Map of paths to their respective hashes for performance's sake, though it may take up too much memory over a long enough span of time.

[nsreed]

Well... CI has spoken. Back to the drawing board.