- "Normal" instead of "NonSpecial"
- "NonLibrary" instead of "2"
I could not find a good replacement for "NonLibrary", nor for "Source",
but I added QLDocs in a few places to help the reading.
- add `getCallable`, `getArg` and `getNode`
- these are `none` for summary calls
- revert "external" uses (they had been changed to `DataFlowSourceCall`)
- Branch predicates are made simple. In particular, they do not try to detect library calls.
- All branches based on `CallNode`s are gathered into one.
- That branch has been given a class `NonSpecialCall`, which is the new parent of call classes based on `CallNode`s. (Those classes now have more involved charpreds.)
- A new such class, 'LambdaCall` has been split out from `FunctionCall` to allow the latter to replace its
general `CallNode` field with a specific `FunctionValue` one.
- `NonSpecialCall` is not an abstract class, but it has some abstract overrides. Therefor, it is not
considered a resolved call in the test `UnresolvedCalls.qll`.
