DS-2514 Packaged version of html5shiv.js is missing "main" element

Added "main" element to html5shiv.js, which should bring it inline
with the 3.6.2pre distribution from aFarkas's Github repo:
https://raw.githubusercontent.com/aFarkas/html5shiv/
3.6.2pre/dist/html5shiv.js

This can be verified by unminifying html5shiv.js in the above link
and html5shiv.js in DSpace master, and comparing them in any merge
program like vimdiff or WinMerge.

Without this patch, IE 8 self-closes the "main" element, and pushes
its child DIVs after it instead of nesting them within itself, which
has repercussions when styling the JSPUI with CSS.

With this patch, IE 8 comprehends the "main" element, and nests the
DIVs correctly.