FLT_MAX requires include <cfloat>
FLT_MAX requires include <cfloat>

Fixes error: 'FLT_MAX' was not declared in this scope.
Tested on gcc 4.7 on armv7 & gcc 4.9 on x64

Signed-off-by: Matthieu Crapet <15bb547ad328b27b95c23c0dca027bbf4a264ca4@gmail.com>

yuanyuanxiang/zxing-cpp,glassechidna/zxing-cpp,glassechidna/zxing-cpp,yuanyuanxiang/zxing-cpp