Advantages:
- it avoids the swig user having to jump through hoops to get print to
work as expected when redefining repr/str slots.
- typing the name of a variable on the python prompt now prints the
result of a (possibly redefined) repr, without the swig user having to
do any extra work.
- when redefining repr, the swig user doesn't necessarily have to
redefine str as it will call the redefined repr
- the behaviour is exactly the same as without the -builtin option while
requiring no extra work by the user (aside from adding the
%feature("python:slot...) statements of course)
- the patch simplifies pyrun.swg a tiny bit.
Disadvantage:
- default str() will give different (but clearer?) output on swigged
classes compared to unpatched swig
SF Bug #326
