GROMACS does not honor when GMX_MAXCONSTRWARN is set to -1
Only one SETTLE error is enough to cause the program to halt when GMX_MAXCONSTRWARN is set to -1. There is no check that I can find that checks if maxwarn is -1. I will add a patch.
Set maxwarn to INT_MAX if GMX_MAXCONSTRWARN < 0
maxwarn is set to the value of the environmental variable
GMX_MAXCONSTRWARN, and we tell users to set that variable to -1 to have
no maximum. This condition was not being checked, so when set to -1 just
1 SETTLE warning was enough to halt the program. This commit fixes
that behavior by setting maxwarn to INT_MAX if GMX_MAXCONSTRWARN is -1
(or any other negative number).