Exit early if we find an inconsistent property.

Further messages about inconsistency are distracting.
Make INTERFACE determined properties readable in generator expressions.

This means setting them after 'configure time' but early in 'generate
time' on the targets themselves.

Add tests for many aspects of COMPATIBLE_INTERFACE_BOOL properties.
Merge topic 'fix-COMPATIBLE_INTERFACE-properties' into next

4b900c0 Make INTERFACE determined properties readable in generator expressions.
d9afacc Exit early if we find an inconsistent property.