Add assertions in IntCastRounded
Add assertions in IntCastRounded

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=39185 could be
caused by an integer overflow in IntCastRounded.

Signed-off-by: Stefan Weil <8d4c780fcfdc41841e5070f4c43da8958ba6aec0@weilnetz.de>

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