Accept upper-case "Chunked" in addition to "chunked" for transfer encoding

Certain clients (particularly Apple's Finder) specify "Chunked" (upper-case)
instead of "chunked" as their desired transfer encoding.

Please confirm that this correctly compares the end of the string.
I don't know if checking the terminating '\0' was necessary. 
I removed it because I didn't find a true 7-character comparison
function among the custom comparators.

This change is needed in order for libevhtp-based webdav servers to 
work with Apple's Finder.