tests: fix memleak in server/resolve.c

This makes LeakSanitizer happy.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
tests: fix libhostname visibility

I noticed that a patched cmake build would pass tests with a fake local
hostname, but the autotools build skips them:

    got unexpected host name back, LD_PRELOAD failed

It turns out that -fvisibility=hidden hides the symbol, and since the
tests are not part of libcurl, it fails too. Just remove the LIBCURL
guard.

Broken since cURL 7.30 (commit 83a42ee20ea7fc25abb61c0b7ef56ebe712d7093,
"curl.h: stricter CURL_EXTERN linkage decorations logic").

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
cmake: fix HAVE_GETHOSTNAME definition

Otherwise Curl_gethostname always fails. Windows has gethostname
since Vista according to
http://msdn.microsoft.com/en-us/library/ms738527%28VS.85%29.aspx, but
accordings to byte_bucket's VC 2005 documentation, it is available even
in Windows 95. (possibly after installing a Platform SDK, the
Windows Server 2003 SP1 Platform SDK should be sufficient).

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
cmake: build libhostname for test suite

Used by some test cases via LD_PRELOAD in order to fake the host name.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
cmake: add ENABLE_THREADED_RESOLVER, rename ARES

Fix detection of the AsynchDNS feature which not just depends on
pthreads support, but also on whether USE_POSIX_THREADS is set or not.
Caught by test 1014.

This patch adds a new ENABLE_THREADED_RESOLVER option (corresponding to
--enable-threaded-resolver of autotools) which also needs a check for
HAVE_PTHREAD_H.

For symmetry with autotools, CURL_USE_ARES is renamed to ENABLE_ARES
(--enable-ares). Checks that test for the availability actually use
USE_ARES instead as that is the result of whether a-res is available or
not (in practice this does not matter as CARES is marked as required
package, but nevertheless it is better to write the intent).

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
symbol-scan.pl: do not require autotools

Makes test1119 pass when building with cmake.

configurehelp.pm is generated by configure (autotools). As cmake does
not provide a separate variable for the C preprocessor, default to cpp.
Before commit ef24ecde68a5f577a7f0f423a767620f09a0ab16 ("symbol-scan:
use configure script knowledge about how to run the C preprocessor"),
this tool would also use 'cpp'.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>