compile time coverage: dmd -staticcov

[timotheecour]

Why not have a -staticcov (or -ctcov) flag to dmd that produces 
compile time code coverage?
This will work for most code (with the exception of virtual 
methods called from a base class -- anything else?): it'll just 
produce 1 or 0 depending for each line compiled in, depending on 
whether it's reachable from main file.

Likewise, with the recent addition of minimal code coverage for 
unittest we could have:

dmd -cov=83 -unittest -main -run std/file.d
dmd -staticcov=83 -unittest -main -run std/file.d

Further enhancements: compile time caller/callee graph.

Thanks for your feedback!