Fix Memory leak when using TESSERACT_IMAGEDATA_AS_PIX
Fix Memory leak when using TESSERACT_IMAGEDATA_AS_PIX

If building with TESSERACT_IMAGEDATA_AS_PIX, then tesseract
doesn't compress/decompress images, but rather holds the
data as internal Pix structures. Unfortunately, I forgot to
make the ImageData destructor free these, so memory leaked
during use. Fixed here.

tesseract-ocr/tesseract,tesseract-ocr/tesseract,amitdo/tesseract,UB-Mannheim/tesseract,amitdo/tesseract,amitdo/tesseract,UB-Mannheim/tesseract,tesseract-ocr/tesseract,stweil/tesseract,UB-Mannheim/tesseract,amitdo/tesseract,UB-Mannheim/tesseract,tesseract-ocr/tesseract,UB-Mannheim/tesseract,stweil/tesseract,stweil/tesseract,amitdo/tesseract,stweil/tesseract,tesseract-ocr/tesseract,stweil/tesseract