Move contents of builtins/* to stdlib/*. This simplifies finding stubs.

stdlib/2.7/zlib.pyi

@@ -0,0 +1,36 @@
+# Stubs for zlib (Python 2.7)
+
+class error(Exception): ...
+
+DEFLATED = ... # type: int
+DEF_MEM_LEVEL = ... # type: int
+MAX_WBITS = ... # type: int
+ZLIB_VERSION = ... # type: str
+Z_BEST_COMPRESSION = ... # type: int
+Z_BEST_SPEED = ... # type: int
+Z_DEFAULT_COMPRESSION = ... # type: int
+Z_DEFAULT_STRATEGY = ... # type: int
+Z_FILTERED = ... # type: int
+Z_FINISH = ... # type: int
+Z_FULL_FLUSH = ... # type: int
+Z_HUFFMAN_ONLY = ... # type: int
+Z_NO_FLUSH = ... # type: int
+Z_SYNC_FLUSH = ... # type: int
+
+def adler32(data: str, value: int = ...) -> int: ...
+def compress(data: str, level: int = ...) -> str: ...
+def crc32(data: str, value: int = ...) -> int: ...
+def decompress(data: str, wbits: int = ..., bufsize: int = ...) -> str: ...
+
+class compressobj:
+    def __init__(level: int = ..., method: int = ..., wbits: int = ..., memlevel: int = ...,
+                 strategy: int = ...) -> None: ...
+    def copy(self) -> "compressobj": ...
+    def compress(self, data: str) -> str: ...
+    def flush(self) -> None: ...
+
+class decompressobj:
+    def __init__(wbits: int = ...) -> None: ...
+    def copy(self) -> "decompressobj": ...
+    def decompress(self, data: str) -> str: ...
+    def flush(self) -> None: ...