Initialize boolean value.
Merge topic 'compile-defs-debugging' into next

3e7b25a Initialize boolean value.
Add target property debugging for COMPILE_DEFINITIONS

Use constructs similar to those for COMPILE_OPTIONS. This is a little
different because there is a command to remove_definitions(), so
we can't populate the equivalent target property until generate-time
in cmGlobalGenerator.
Merge topic 'compile-defs-debugging' into next

5a7f8b8 Add target property debugging for COMPILE_DEFINITIONS