resolve #154 - fix temp file handling for multiple part uploads

concatenate the name of the file (be it POSTDATA, PUTDATA, or the
name defined as part of the upload, or if not present the actual
file name on disk) into the hash key to ensure we get one entry in
.tmpfiles per actual file and don't overwrite any existing entries
in the hash with others. thanks to GeJ for the test case

dump version and Changes