System-Sources depends on AST-Core

[jecisc]

We have a bad dependency. In the current bootstrap System-Sources needs to be loaded before the AST. But it currently depends on the AST in some places.

• SourceFileArray>>#timeStampAt:for:
• SourceFileArray>>#protocolAt:for:

Both those methods are using OCParser from AST-Core

For now I am not sure what is the best solution to fix this dependency problem