Remove any whitespace before ignored Doxygen commands.

This is done mainly to avoid problems with trailing whitespace in the
generated Python code as this provokes pep8 problems, but is also, arguably,
more logical, as if a command which is on its own on a line is ignored, we
shouldn't leave any whitespace neither (and perhaps should even suppress the
line entirely, in fact).

Examples/test-suite/python/doxygen_ignore_runme.py

@@ -7,11 +7,11 @@ commentVerifier.check(doxygen_ignore.func.__doc__,
     r"""
     A contrived example of ignoring too many commands in one comment.
 
-    
 
-    
 
-    
+
+
+
     This is specific to **Python**.