Improve Python 2.7 inspect stub

This patch consists of:

* Splitting and reordering the content into sections corresponding
  to the module's documentation sections
* Implementing some missing functions
* Adding TODOs for missing stuff (I may've missed something)

The signature of isgenerator() (was: Any argument, is: argument of type
object) is changed for consistency with other is* functions I added
here, after some considerations I couldn't decide whether it should be
object or Any - if object is not advised please let me know.

stdlib/2.7/inspect.pyi

@@ -1,14 +1,53 @@
 # TODO incomplete
-from typing import Any, List, Tuple, NamedTuple
+from types import TracebackType, FrameType, ModuleType
+from typing import Any, Callable, List, Optional, Tuple, NamedTuple
 
-def isgenerator(object: Any) -> bool: ...
+# Types and members
+ModuleInfo = NamedTuple('ModuleInfo', [('name', str),
+                                       ('suffix', str),
+                                       ('mode', str),
+                                       ('module_type', int),
+                                       ])
+def getmembers(object: object,
+               predicate: Callable[[Any], bool] = ...,
+               ) -> List[Tuple[str, object]]: ...
+def getmoduleinfo(path: str) -> Optional[ModuleInfo]: ...
+def getmodulename(path: str) -> Optional[str]: ...
 
-class _Frame:
-    ...
-_FrameRecord = Tuple[_Frame, str, int, str, List[str], int]
+def ismodule(object: object) -> bool: ...
+def isclass(object: object) -> bool: ...
+def ismethod(object: object) -> bool: ...
+def isfunction(object: object) -> bool: ...
+def isisgeneratorfunction(object: object) -> bool: ...
+def isgenerator(object: object) -> bool: ...
+def istraceback(object: object) -> bool: ...
+def isframe(object: object) -> bool: ...
+def iscode(object: object) -> bool: ...
+def isbuiltin(object: object) -> bool: ...
+def isroutine(object: object) -> bool: ...
+def isabstract(object: object) -> bool: ...
+def ismethoddescriptor(object: object) -> bool: ...
+def isdatadescriptor(object: object) -> bool: ...
+def isgetsetdescriptor(object: object) -> bool: ...
+def ismemberdescriptor(object: object) -> bool: ...
 
-def currentframe() -> _FrameRecord: ...
-def stack(context: int = ...) -> List[_FrameRecord]: ...
+# Retrieving source code
+def getdoc(object: object) -> str: ...
+def getcomments(object: object) -> str: ...
+def getfile(object: object) -> str: ...
+def getmodule(object: object) -> ModuleType: ...
+def getsourcefile(object: object) -> str: ...
+# TODO restrict to "module, class, method, function, traceback, frame,
+# or code object"
+def getsourcelines(object: object) -> Tuple[List[str], int]: ...
+# TODO restrict to "a module, class, method, function, traceback, frame,
+# or code object"
+def getsource(object: object) -> str: ...
+def cleandoc(doc: str) -> str: ...
+
+# Classes and functions
+# TODO make the return type more specific
+def getclasstree(classes: List[type], unique: bool = ...) -> Any: ...
 
 ArgSpec = NamedTuple('ArgSpec', [('args', List[str]),
                                  ('varargs', str),
@@ -17,3 +56,23 @@ ArgSpec = NamedTuple('ArgSpec', [('args', List[str]),
                                  ])
 
 def getargspec(func: object) -> ArgSpec: ...
+# TODO make the return type more specific
+def getargvalues(frame: FrameType) -> Any: ...
+# TODO formatargspec
+# TODO formatargvalues
+def getmro(cls: type) -> Tuple[type, ...]: ...
+# TODO getcallargs
+
+# The interpreter stack
+# TODO getframeinfo
+# TODO getouterframes
+def getinnerframes(traceback: TracebackType, context: int = ...) -> List[FrameType]:
+    ...
+
+class _Frame:
+    ...
+_FrameRecord = Tuple[_Frame, str, int, str, List[str], int]
+
+def currentframe() -> _FrameRecord: ...
+def stack(context: int = ...) -> List[_FrameRecord]: ...
+def trace(context: int = ...) -> List[_FrameRecord]: ...