[Lazarus] New compiler options page "Additions and Overrides"

[Michael Schnell]

Looks like a really nice update.

Sorry for my ignorance, but
  - what exactly is meant by "target" and how I choose between multiple 
targets ?
  - Why can multiple "target" lines be present at the same time ?
  - What is the use of the green vs the white macro activation check box ?
  - I suppose, the result of this page can be stored as a "build mode", 
but I don't find how to create, store or load a "build mode"


Thanks,
-Michael