Adds a new 'key.retrieve_symbol_graph' option to the request. When set to 1 it
includes the JSON for a SymbolGraph containing a single node for the symbol at
the requested position.
This also extends the SymbolGraph library with a new entry point to get a graph
for a single symbol, and to additionally support type substitution to match the
existing CursorInfo behavior (e.g. so that when invoked on `first` in
`Array<Int>().first`, the type is given as `Int?` rather than `Element?`).
Resolves rdar://problem/70551509
Previously 'isSystemModule()' returns true only if the module is:
- Standard library
- Clang module and that is `IsSystem`
- Swift overlay for clang `IsSystem` module
Now:
- Clang module and that is `IsSystem`; or
- Swift overlay for clang `IsSystem` module
- Swift module found in either of these directories:
- Runtime library directoris (including stdlib)
- Frameworks in `-Fsystem` directories
- Frameworks in `$SDKROOT/System/Library/Frameworks/` (Darwin)
- Frameworks in `$SDKROOT/Library/Frameworks/` (Darwin)
rdar://problem/50516314
