Allow specifying a revision to stop at using the -H flag. This is useful for converting repositories which have been deleted or renamed, such as llvm-gcc-4-2 in the LLVM repositories which was renamed to llvm-gcc-4.2 shortly after its creation. Also, consolidate the two places in svn_swig_wrapper.py where a default chunk size is specified to one, single variable declaration.

import sys
import os
sys.path.append(os.path.dirname(os.path.dirname(__file__)))