Fixed problems in testing addition operations
More carefully defined the concepts.  That is the concept of the library is now clear:

Trap at either compile or runtime integer operations which yield a result which differs from the normal arithmetic result.

Pending on this check in:
a) only addition is fixed up so far
b) uses BOOST_TYPEOF... rather than decltype(... - final decision sill pending.
c) comments out some compile time checks which should be re-instated.
d) fixed tests so that they actually work!
Got all tests for subtraction to pass.
intermediat changes
almost have safe multiplication working.  Fails 4 test cases.  BUT these cases require more than trivial changes so I'm checking in this intermediate version
working:
test_multiply
test_cast
working
test add
test cast
test compare
test conversion
test subtract
test multiply
test divide passes
test_modulus
improvements to logical/shift operations
improve local operations - no tests for these yet
fix subtraction
passes all tests
adjustments to make test_conversion pass
All tests pass in Debug and Release!!!