Remove ETL_ERROR and replaced with ETL_ASSERT.
ETL_ASSERT will eveluate to 'true' in all cases except for error logging.
This will allow 'if' statements that contain the macro to be optimised away for all cases except logging.
Added ETL_NO_CHECKS and ETL_LOG_ERRORS macro checks.
The options are now:-
ETL_NO_CHECKS ETL_ASSERT does nothing. Evaluates to 'true'.
ETL_THROW_EXCEPTIONS) ETL_ASSERT throws an exception if the condition fails. Evaluates to 'true'.
ETL_LOG_ERRORS ETL_ASSERT logs the error if the condition fails. Evaluates to the result of the condition.
If none of the above are defined:-
NDEBUG ETL_ASSERT does nothing. Evaluates to 'true'.
Otherwise:-
ETL_ASSERT asserts if the condition fails. Evaluates to 'true'.
