XMI21 — section 7.10.2.2(.2) on page 23 (editorial)

I've posted these to the XMI 2.1 RTF before. Since these typos still
exist in the MOF2XMI Final Adopted Spec (ptc/03-11-04), I figured I
should send them again. As editorial issues, they were not assigned
an official issue number.

In section 7.10.2.2(.2) on page 23, the URN for the XMI namespace
needs to be in lowercase, according to W3C. Thus, change

xmlns:xlink="http://www.w3.org/1999/XLink"

to

xmlns:xlink="http://www.w3.org/1999/xlink"