The ppm spec allows 1-bit ascii ppm files to have no spaces bitween the
single bits. Therefore we have to adjust read_pbm_int() to stop after
reading one digit.
Pick-to: 6.6
Fixes: QTBUG-119239
Change-Id: I161038076c5dee4662aa66a1215822fc75e6a19e
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>