Replay: added floating point exception checking

allows NaN errors to be caught in gdb
AP_AHRS: prevent a infinity value
AP_Math: prevent a floating point exception
AP_NavEKF: catch covarience errors and reset filter

this catches covariance values beyond a reasonable limit and resets
the filter is they happen
SITL: added SIM_FLOAT_EXCEPT parameter

this enables checking for floating point exceptions
HAL_SITL: enable use of SIM_FLOAT_EXCEPT parameter