FindAndRemoveLines/FindVerticalAlignment: decrease fixed vline min length
FindAndRemoveLines/FindVerticalAlignment: decrease fixed vline min length

When detecting vertical separators, the blob aligner is used to glue
line segments (often segmented due to artificial cracks).
But (unlike LineFinder) it has many parameters that are not
relative to pixel density/resolution.
This change decreases the minimum absolute length in pixels
for vertical separators.

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