* Do not warn about size mismatch on responses without a Content-Length:

* Do not warn about size mismatch on responses without a Content-Length:
header
* Documented all the options in usage().
* Added -t to build a tracefile suitable for later input

A tracefile has the format

METHOD URL BODY-FILE SIZE CHECKSUM
Where:
METHOD          Is the HTTP method to use, usually GET
URL             The URL
BODY-FILE       Is a file to send as request body (- for none)
SIZE            The object size of the returned object (- to ignore)
CHECKSUM        A simple checksum of the object (- to ignore)

tcp-banger already accepts this format as input (was in one of my
previous tcp-banger patches).

/Henrik