function getHeaderValue(sHeaders, sHeaderName) {
		var aHeaderParts,
			aHeaders = sHeaders.split("\r\n"),
			i;

		for (i = 0; i < aHeaders.length; i += 1) {
			aHeaderParts = aHeaders[i].split(":");

			if (aHeaderParts[0].toLowerCase().trim() === sHeaderName) {
				return aHeaderParts[1].trim();
			}
		}
	}
Returns value of the header with the specified <code>sHeaderName</code> from
the specified <code>sHeaders</code> section of MIME part.

@param {string} sHeaders
  Section of MIME part representing HTTP headers
@param {string} sHeaderName
  Name of HTTP header in lower case
@returns {string|undefined} The HTTP header value or <code>undefined</code>