[IronPython] RE_Match.start with named group

[Sanghyeon Seo]

# test.py
import re
match = re.match(r'(?P<test>test)', 'test')
print match.span('test')
print match.start('test')
print match.end('test')

Only the second print raises.

This is trivial to fix. At re.cs line 552:

-public int Start(int group) {
+public int Start(object group) {

Seo Sanghyeon