Fix most trivially-findable print statements.

There's one major and one minor category still unfixed:
doctests are the major category (and I hope to be able to augment the
refactoring tool to refactor bona fide doctests soon);
other code generating print statements in strings is the minor category.

(Oh, and I don't know if the compiler package works.)
diff --git a/Lib/atexit.py b/Lib/atexit.py
index 93fddf7..51a153e 100644
--- a/Lib/atexit.py
+++ b/Lib/atexit.py
@@ -26,7 +26,7 @@
             exc_info = sys.exc_info()
         except:
             import traceback
-            print >> sys.stderr, "Error in atexit._run_exitfuncs:"
+            print("Error in atexit._run_exitfuncs:", file=sys.stderr)
             traceback.print_exc()
             exc_info = sys.exc_info()
 
@@ -53,11 +53,11 @@
 
 if __name__ == "__main__":
     def x1():
-        print "running x1"
+        print("running x1")
     def x2(n):
-        print "running x2(%r)" % (n,)
+        print("running x2(%r)" % (n,))
     def x3(n, kwd=None):
-        print "running x3(%r, kwd=%r)" % (n, kwd)
+        print("running x3(%r, kwd=%r)" % (n, kwd))
 
     register(x1)
     register(x2, 12)