Adds a missing call to addLazyPathDependenciesOnly in
std.Build.Module.addCSourceFiles. Also fixes an issue in
std.Build.Step.WriteFile where it wasn't updating all the GeneratedFile
instances for every directory. To fix the second issue, I removed
all the GeneratedFile instances and now all files/directories reference
the steps main GeneratedFile via sub paths.
* make test names contain the fully qualified name
* make test filters match the fully qualified name
* allow multiple test filters, where a test is skipped if it does not
match any of the specified filters
