* master: (27 commits)
  Don't call --strict-optional and --incremental experimental (python#4642)
  Sync typeshed (python#4641)
  Fix callable types with inconsistent argument counts (python#4611)
  Fix example (add 'class A:')
  Make psutil an optional dependency (python#4634)
  mypy and mypy_extensions aren't posix only (python#3765)
  Documentation for attr support (python#4632)
  Use read_with_python_encoding in stubgen to handle file encoding (python#3790)
  Sync typeshed (python#4631)
  Add remaining core team emails to CREDITS (python#4629)
  Fix issues with attr code. (python#4628)
  Better support for converter in attrs plugin. (python#4607)
  Clean up credits (python#4626)
  Support type aliases in fine-grained incremental mode (python#4525)
  Fine-grained: Fix crash caused by unreachable class (python#4613)
  Treat divmod like a binary operator (python#4585)
  Sync typeshed (python#4605)
  Fine-grained: Don't infer partial types from multiple targets (python#4553)
  Fine-grained: Compare symbol table snapshots when following dependencies (python#4598)
  Fix type of forward reference to a decorated class method (python#4486)
  ...

…ies (python#4598)

Previously we just compared symbol table node types, which would fail to
propagate certain changes. For example, we could fail to detect a change
from a module reference to a normal variable.

This only affects detecting changes when we are propagating changes using
fine-grained dependencies. Snapshot comparison was already being used
when processing an entire module.

Fixes python#4595.