[CoinUtils] coin utils warnings

[Matthew Galati]

Can someone please cleanup these warnings?

Thanks,
Matt

../../../CoinUtils/src/CoinModel.cpp: In member function 'void 
CoinModel::addRow(int, const int*, const double*, double, double, const 
char*)':
../../../CoinUtils/src/CoinModel.cpp:614: warning: conversion to 
'unsigned int:31' from 'unsigned int' may alter its value
../../../CoinUtils/src/CoinModel.cpp: In member function 'void 
CoinModel::addColumn(int, const int*, const double*, double, double, 
double, const c\
har*, bool)':
../../../CoinUtils/src/CoinModel.cpp:752: warning: conversion to 
'unsigned int:31' from 'unsigned int' may alter its value
../../../CoinUtils/src/CoinModel.cpp: In member function 'int 
CoinModel::packRows()':
../../../CoinUtils/src/CoinModel.cpp:1430: warning: conversion to 
'unsigned int:31' from 'unsigned int' may alter its value
../../../CoinUtils/src/CoinModelUseful.cpp: In member function 'int 
CoinModelLinkedList::addEasy(int, int, const int*, const double*, 
CoinModelTrip\
le*, CoinModelHash2&)':
../../../CoinUtils/src/CoinModelUseful.cpp:1010: warning: conversion to 
'unsigned int:31' from 'unsigned int' may alter its value
../../../CoinUtils/src/CoinModelUseful.cpp:1015: warning: conversion to 
'unsigned int:31' from 'unsigned int' may alter its value
../../../CoinUtils/src/CoinModelUseful.cpp: In member function 'void 
CoinModelLinkedList::addHard(int, int, const int*, const double*, 
CoinModelTri\
ple*, CoinModelHash2&)':
../../../CoinUtils/src/CoinModelUseful.cpp:1071: warning: conversion to 
'unsigned int:31' from 'unsigned int' may alter its value
../../../CoinUtils/src/CoinModelUseful.cpp:1076: warning: conversion to 
'unsigned int:31' from 'unsigned int' may alter its value