Left-shifts of negative values are undefined in C++. In particular,
they don't behave arithmetically.
Reported by UBSan:
qgrayraster.c:510:19: runtime error: left shift of negative value -1/-42
qgrayraster.c:537:26: runtime error: left shift of negative value -1/-4/-128
qgrayraster.c:538:26: runtime error: left shift of negative value -1/-4/-128
qgrayraster.c:641:28: runtime error: left shift of negative value -1/-42
qgrayraster.c:676:44: runtime error: left shift of negative value -1/-4/-5/-14/-129
qgrayraster.c:807:19: runtime error: left shift of negative value -1/-42
qgrayraster.c:1101:9: runtime error: left shift of negative value -32/-46/-224/-8160
qgrayraster.c:1102:9: runtime error: left shift of negative value -32/-2626
qgrayraster.c:1454:36: runtime error: left shift of negative value -32/-96/-224/-466/-2626/-8160
qgrayraster.c:1535:30: runtime error: left shift of negative value -32/-46/-224/-2626/-8160
Fix by using ordinary multiplication instead, because negative
left-hand-side values don't look like they are an error.
Change-Id: I2e96de51adb4a030de8a49869ddd98a31dab31b3
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>