add py2 stubs for dis (by moving them into 2and3) (#1033)

Only a few functions were added in early py3 relative to py2, so it seems
fine to use a single stub. 3.4 made bigger API changes.

stdlib/2and3/dis.pyi

@@ -0,0 +1,75 @@
+from typing import List, Union, Iterator, Tuple, Optional, Any, IO, NamedTuple, Dict
+
+import sys
+import types
+
+from opcode import (hasconst as hasconst, hasname as hasname, hasjrel as hasjrel,
+                    hasjabs as hasjabs, haslocal as haslocal, hascompare as hascompare,
+                    hasfree as hasfree, cmp_op as cmp_op, opname as opname, opmap as opmap,
+                    HAVE_ARGUMENT as HAVE_ARGUMENT, EXTENDED_ARG as EXTENDED_ARG)
+
+if sys.version_info >= (3, 4):
+    from opcode import stack_effect as stack_effect
+
+if sys.version_info >= (3, 6):
+    from opcode import hasnargs as hasnargs
+
+_have_code = Union[types.MethodType, types.FunctionType, types.CodeType, type]
+_have_code_or_string = Union[_have_code, str, bytes]
+
+
+if sys.version_info >= (3, 4):
+    Instruction = NamedTuple(
+        "Instruction",
+        [
+            ('opname', str),
+            ('opcode', int),
+            ('arg', Optional[int]),
+            ('argval', Any),
+            ('argrepr', str),
+            ('offset', int),
+            ('starts_line', Optional[int]),
+            ('is_jump_target', bool)
+        ]
+    )
+
+    class Bytecode:
+        codeobj = ...  # type: types.CodeType
+        first_line = ...  # type: int
+        def __init__(self, x: _have_code_or_string, *, first_line: Optional[int] = ...,
+                     current_offset: Optional[int] = ...) -> None: ...
+        def __iter__(self) -> Iterator[Instruction]: ...
+        def __repr__(self) -> str: ...
+        def info(self) -> str: ...
+        def dis(self) -> str: ...
+
+        @classmethod
+        def from_traceback(cls, tb: types.TracebackType) -> Bytecode: ...
+
+
+COMPILER_FLAG_NAMES = ...  # type:  Dict[int, str]
+
+
+def findlabels(code: _have_code) -> List[int]: ...
+def findlinestarts(code: _have_code) -> Iterator[Tuple[int, int]]: ...
+
+if sys.version_info >= (3, 0):
+    def pretty_flags(flags: int) -> str: ...
+    def code_info(x: _have_code_or_string) -> str: ...
+
+if sys.version_info >= (3, 4):
+    def dis(x: _have_code_or_string = ..., *, file: Optional[IO[str]] = ...) -> None: ...
+    def distb(tb: Optional[types.TracebackType] = ..., *, file: Optional[IO[str]] = ...) -> None: ...
+    def disassemble(co: _have_code, lasti: int = ..., *, file: Optional[IO[str]] = ...) -> None: ...
+    def disco(co: _have_code, lasti: int = ..., *, file: Optional[IO[str]] = ...) -> None: ...
+    def show_code(co: _have_code, *, file: Optional[IO[str]] = ...) -> None: ...
+
+    def get_instructions(x: _have_code, *, first_line: Optional[int] = ...) -> Iterator[Instruction]: ...
+else:
+    def dis(x: _have_code_or_string = ...) -> None: ...
+    def distb(tb: types.TracebackType = ...) -> None: ...
+    def disassemble(co: _have_code, lasti: int = ...) -> None: ...
+    def disco(co: _have_code, lasti: int = ...) -> None: ...
+
+    if sys.version_info >= (3, 0):
+        def show_code(co: _have_code) -> None: ...