Improve random hash generator with openssl_random_pseudo_bytes
filetype: gettype() now favours "less safe" types
filetype: Identify some new file types (mp3/flac)
filetype: add getextension + improve mime types
filetype: add very rough text/plain detection
filetype: fix typo with PHP type
filetypes: fix recognition of gzip files
filetype: fix error with 0-length file