[REGRESSION FIX] gdal_retile.py broken with python 2.X; Restore original output of print statements

[rouault]

Several issues :

1) Major : The 2to3.py conversion script introduced an incompatible form of print statement for python 2.X on gdal_retile.py that prevent execution from the python parser.

Namely : " print 'a', " with the comma at the end to prevent new line output. The python 3.X equivalent is " print('a', end=' ') " which is unrecognized by python 2.X.

2) Minor : gdal_retile.py did not work with Python 3.X because of change in semantic in division of integer variables.

Python 2.X :
>>> a = 1
>>> b = 2
>>> print(a/b)
0

Python 3.X :
>>> a = 1
>>> b = 2
>>> print(a/b)
0.5

3) Minor : the conversion script transformed " print 'a', param " into " print('a', param) " which has not the same output

[rouault]

Fixed in trunk (r18952, r18954) and in branches/1.7 (r18953, r18955)

Add testing of gdal_retile.py in autotest infrastructure in trunk (r18958, r18959)