Simplify tests.
Update .gitignore.
Test .nl reader.
More tests.
Implement NLReader.
Move ExprFactory to a separate header and create a test for it.
nlreader -> nl
More tests.
Move ReplaceLine to util.{h,cc}.
Output arith flags when writing NLHeader.
Implement ExprFactory.
Add ASLBuilder.
Merge InitASL with ASLBuilder. Get rid of GetASL. More tests.
Test ASLBuilder.
Add a TODO item.