Add test_main() functions to various tests where it was simple to do. Done so
that regrtest can execute the test_main() directly instead of relying on import
side-effects.
diff --git a/Lib/test/test_imgfile.py b/Lib/test/test_imgfile.py
index 11311c4..ecc02ea 100755
--- a/Lib/test/test_imgfile.py
+++ b/Lib/test/test_imgfile.py
@@ -9,20 +9,6 @@
 import imgfile, uu
 
 
-def main():
-
-    uu.decode(findfile('testrgb.uue'), 'test.rgb')
-    uu.decode(findfile('greyrgb.uue'), 'greytest.rgb')
-
-    # Test a 3 byte color image
-    testimage('test.rgb')
-
-    # Test a 1 byte greyscale image
-    testimage('greytest.rgb')
-
-    unlink('test.rgb')
-    unlink('greytest.rgb')
-
 def testimage(name):
     """Run through the imgfile's battery of possible methods
        on the image passed in name.
@@ -113,4 +99,20 @@
 
     os.unlink(outputfile)
 
-main()
+
+def test_main():
+
+    uu.decode(findfile('testrgb.uue'), 'test.rgb')
+    uu.decode(findfile('greyrgb.uue'), 'greytest.rgb')
+
+    # Test a 3 byte color image
+    testimage('test.rgb')
+
+    # Test a 1 byte greyscale image
+    testimage('greytest.rgb')
+
+    unlink('test.rgb')
+    unlink('greytest.rgb')
+
+if __name__ == '__main__':
+    test_main()