Heap out-of-bounds read in DCMTK RLE decodeFrame()

A heap-based out-of-bounds read in DcmRLECodecDecoder::decodeFrame() in dcmdata/libsrc/dcrleccd.cc of OFFIS DCMTK 3.7.0 allows an attacker to read up to 63 bytes of adjacent heap memory, or cause a crash, via a crafted RLE Lossless DICOM file whose pixel data fragment is shorter than the 64-byte RLE header. The function copies 64 bytes without checking the fragment length, a check that the sibling function decode() already performs. Applications that decode RLE images frame by frame (for example, through DcmPixelData::getUncompressedFrame()) are affected. The dcmdrle command-line tool uses decode() and is not affected. The issue is fixed in commit 45469f3c30037e9c7159290e4bb74cd7b3b9ef1d.