bpo-33656: On Windows, add API call saying that tk scales for DPI (GH-7137)

On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary
unchanged, and a monitor resolution greater than 96 DPI, this should
make text and lines sharper. It should otherwise have no effect.

Using a magnifier, I determined that the improvement comes from horizontal and
lines being better lined up with the monitor pixels. I checked that this call causes
no problem on any Windows buildbot, including the Win7 buildbots. Unlike most
IDLE patches, this one can be easily reverted by users by removing a few lines,
at the top of idlelib/pyshell.py.

Lib/idlelib/pyshell.py

@@ -8,6 +8,14 @@ except ImportError:
     print("** IDLE can't import Tkinter.\n"
           "Your Python may not be configured for Tk. **", file=sys.__stderr__)
     raise SystemExit(1)
+
+if sys.platform == 'win32':
+    import ctypes
+    try:
+        ctypes.OleDLL('shcore').SetProcessDpiAwareness(1)
+    except (AttributeError, OSError):
+        pass
+
 import tkinter.messagebox as tkMessageBox
 if TkVersion < 8.5:
     root = Tk()  # otherwise create root in main