Improve several stubs. (math, _random, time, etc.)

Some of these are derived from mypy/stubs/.

2.7/time.pyi

@@ -1,32 +1,46 @@
 """Stub file for the 'time' module."""
-# This is an autogenerated file. It serves as a starting point
-# for a more precise manual annotation of this module.
-# Feel free to edit the source below, but remove this header when you do.
+# See https://docs.python.org/2/library/time.html
 
-from typing import Any, List, Tuple, Dict, GenericType
+from typing import NamedTuple, Tuple, Union
 
-def asctime(*args, **kwargs) -> str:
+# ----- variables and constants -----
+accept2dyear = False 
+altzone = 0
+daylight = 0
+timezone = 0
+tzname = ... # type: Tuple[str, str]
+
+struct_time = NamedTuple('struct_time',
+                         [('tm_year', int), ('tm_mon', int), ('tm_mday', int),
+                          ('tm_hour', int), ('tm_min', int), ('tm_sec', int),
+                          ('tm_wday', int), ('tm_yday', int), ('tm_isdst', int)])
+
+_TIME_TUPLE = Tuple[int, int, int, int, int, int, int, int, int]
+
+def asctime(t: struct_time = None) -> str:
     raise ValueError()
 
 def clock() -> float: ...
 
-def ctime(*args, **kwargs) -> str:
+def ctime(secs: float = None) -> str:
     raise ValueError()
 
-def gmtime(*args, **kwargs) -> tuple: ...
+def gmtime(secs: float = None) -> struct_time: ...
 
-def localtime(*args, **kwargs) -> tuple: ...
+def localtime(secs: float = None) -> struct_time: ...
 
-def mktime(*args, **kwargs) -> float:
+def mktime(t: struct_time) -> float:
     raise OverflowError()
+    raise ValueError()
 
-def sleep(a: float) -> None: ...
+def sleep(secs: float) -> None: ...
 
-def strftime(a: str, *args, **kwargs) -> str:
+def strftime(format: str, t: struct_time = None) -> str:
     raise MemoryError()
     raise ValueError()
 
-def strptime(*args, **kwargs) -> Any: ...
+def strptime(string: str, format: str = "%a %b %d %H:%M:%S %Y") -> struct_time:
+    raise ValueError()
 
 def time() -> float:
     raise IOError()