Datalist polyfill: Fixed polyfill so only displays value if value and label are identical and also corrected undefined checks (fixes #2823 and supercedes #2831).
Merge pull request #2835 from pjackson28/datalistfix

Datalist polyfill: Fixed polyfill so only displays value if value and label are identical and also corrected undefined checks (fixes #2823 and supercedes #2831)
Corrected left mouse button detection for pre-IE9 (fixes #2836).
Merge pull request #2841 from pjackson28/leftmousebuttonfix

Corrected left mouse button detection for pre-IE9 (fixes #2836)
Resolved merge conflict