Add types to some cross-platform functions in the platform library (#2781)

stdlib/2/platform.pyi

@@ -2,7 +2,7 @@
 #
 # Based on stub generated by stubgen.
 
-from typing import Any, Optional
+from typing import Any, Optional, Tuple
 
 __copyright__ = ...  # type: Any
 DEV_NULL = ...  # type: Any
@@ -27,19 +27,19 @@ def win32_ver(release=..., version=..., csd=..., ptype=...): ...
 def mac_ver(release=..., versioninfo=..., machine=...): ...
 def java_ver(release=..., vendor=..., vminfo=..., osinfo=...): ...
 def system_alias(system, release, version): ...
-def architecture(executable=..., bits=..., linkage=...): ...
-def uname(): ...
-def system(): ...
-def node(): ...
-def release(): ...
-def version(): ...
-def machine(): ...
-def processor(): ...
-def python_implementation(): ...
-def python_version(): ...
-def python_version_tuple(): ...
-def python_branch(): ...
-def python_revision(): ...
-def python_build(): ...
-def python_compiler(): ...
-def platform(aliased: int = ..., terse: int = ...): ...
+def architecture(executable=..., bits=..., linkage=...) -> Tuple[str, str]: ...
+def uname() -> Tuple[str, str, str, str, str, str]: ...
+def system() -> str: ...
+def node() -> str: ...
+def release() -> str: ...
+def version() -> str: ...
+def machine() -> str: ...
+def processor() -> str: ...
+def python_implementation() -> str: ...
+def python_version() -> str: ...
+def python_version_tuple() -> Tuple[str, str, str]: ...
+def python_branch() -> str: ...
+def python_revision() -> str: ...
+def python_build() -> Tuple[str, str]: ...
+def python_compiler() -> str: ...
+def platform(aliased: int = ..., terse: int = ...) -> str: ...