Links with # in directory (eg, Twitter) are classed as not valid

I was trying to add twitter links to my site, these are now in the format http://twitter.com/#!/profilename. However, these are being flagged as not valid. After a bit of digging round, I found the problem seemed to be with line 742 in link.module:-

 $directories = "(\/[a-z0-9_\-\.~+%=&,$'!():;*@\[\]]*)*";

Which I have added a # to, to make:-

 $directories = "(\/[a-z0-9_\-\.~+%=&,$'#!():;*@\[\]]*)*";

However, I do not know how to create a patch.