[CentOS] announcement topics

i did some searching in the mailman code and have discovered that mailman
uses the VERBOSE flag to the python regular expression package, which
means that unescaped spaces in the regular expression are ignored.  so you
need to change the topics to be like:

CentOS\ 4\ i386
or:
CentOS[ ]4[ ]i386

i'm not sure how many backslashes will be necessary to make it through to
the module correctly, so brackets may be easier.  or you could change the
subject line format to be more like:

CentOS-4-i386

so you could match without spaces.