[PATCH] Interpreted Range memory leak (3.0 only)

Prevent memory leaks when interpreting Range requests.

HttpRequest::range field could be set to a new HttpHdrRange object
twice: once in clientInterpretRequestHeaders() and once in
HttpRequest::hdrCacheInit() called from HttpRequest::parseHeader().

HttpRequest::range field could be cleared without destroying
HttpHdrRange object in clientInterpretRequestHeaders().

The range field is essentially a cached value of the parsed Range
header. Managing the cache outside its owner object is a bad idea.