- add `getCallable`, `getArg` and `getNode`
- these are `none` for summary calls
- revert "external" uses (they had been changed to `DataFlowSourceCall`)
Two classes have been inserted into the hierarchies:
- `NonLibraryDataFlowCallable` with a method `getACall2`.
This method implements "get a call, not considering flow summaries".
For `NonLibraryDataFlowCallable`s, `getACall` will defer to `getACall2`.
While you could have a synthesised call to such a callable,
it would not correspond to a `CallNode`.
- `NonLibraryDataFlowSourceCall` with methods
`getArg2` and `getCallable2`. These also refer to a call graph that
does not consider flow summaries.
`getArg2` is used to synthesise pre-update nodes for arguments.
`getCallable2` is used in `connects` to compute argument passing.
This is used to define data flow nodes for overflow arguments.
`getACall2` ensures that `LibraryCallableValue::getACall` is not called
when the charpred of `FunctionCall` is evaluated.
The two queries in CWE-020 are used for manual evaluation (is my
understanding), and the two IDE queries should work based on their tags,
and not on the query-id.
