Refine inheritance of Statement types.
Refine inheritance of Statement types.

* dpy/compiler/dast.py

  - (BlockStatement): Rename to 'CompoundStmt'.

  - (Program, InteractiveProgram, Function, ClassStmt, WhileStmt,
    ForStmt, TryStmt, AwaitStmt, WithStmt, Process): Inherit from
    CompoundStmt.

  - (NoopStmt, AssignmentStmt, ReturnStmt, DeleteStmt, YieldStmt,
    YieldFromStmt, RaiseStmt, BreakStmt, PassStmt, ContinueStmt,
    SendStmt, OutputStmt): Inherit from CompoundStmt.

sghosh1991/distalgo,mayli/DistAlgo,mayli/DistAlgo,sghosh1991/distalgo