The `ISC_OVERFLOW_XXX()` macros are usually wrappers around `__builtin_xxx_overflow()`, with alternative implementations for compilers that lack the builtins. Replace the overflow checks in `isc/time.c` with the new macros.
The `ISC_OVERFLOW_XXX()` macros are usually wrappers around `__builtin_xxx_overflow()`, with alternative implementations for compilers that lack the builtins. Replace the overflow checks in `isc/time.c` with the new macros.