Simplify check for NEED_MALLOC_H, and make more explicit that NEED_MALLOC_H shall be defined if <malloc.h> header file must be included even when including <stdlib.h>.

Curl_freeaddrinfo() and Curl_ip2addr().

problem added with the curl_formget() patch.

file: URLs only.

-Log errno in message if setsockopt() fails.

-Close listener socket on major errors.

we did wrong and patched it: When nodes were removed from the splay tree,
and we didn't properly remove it from the splay tree when an easy handle was
removed from a multi stack and thus we could wrongly leave a node in the
splay tree pointing to (bad) memory.

tests/libtest/lib506.c version 1.11 is now also logging CURLSHOPT_LOCKFUNC, CURLSHOPT_UNLOCKFUNC and CURLSHOPT_USERDATA, so we now also have to check them here.