add 'headers=' in client formpost

Reminder for the future: when we're using malloc() we MUST include <stdlib.h>
as otherwise 64bit archs go bananas.

Bug report #517687

was an extra CRLF added to the post data

content-type header, it was used for each part and thus without this it
failed MISERABLY. *smacks forhead*

accordingly

Added most of the Customizing Operations chapter

Forgot one case. On HP-UX 11.00, gethostbyname_r() is properly defined
if -D_REENTRANT is used. Without it, the compiler still accepts the
function prototype but gives a warning about hostent_data going out of
scope. This is because struct hostent_data is not declared. So, we
force an error by trying to set a variable to the struct.

on my test machine! :-)