ProjectPart macros as a semantic structure

Now:

[FOO=bar] -> "#define FOO bar" -> "-DFOO=bar"

Maybe it would be more effective:

[FOO=bar] -> "-DFOO=bar"

So we don't need our own parser.

I would recommend to add an extra variable to ProjectPart which hold the define as a vector of records which describe a define. So it would much easier to compare them.