tests: delete libhostname.so and chkhostname

Before this patch, `libhostname.so` and `chkhostname` were a test
facility for overriding `gethostname()` in non-debug builds on
Linux and other Unix platforms supporting `LD_PRELOAD`.

`gethostname()` has a single use with SMTP.

The alternative way to override `gethostname()` is building in debug
mode, which allows to do this via the `CURL_GETHOSTNAME` env, on all
platforms.

Drop the `LD_PRELOAD` solution in favour of the above.

Also:
- delete inactive NTLM code with a `gethostname()` call made from it.
- streamline NTLM code by dropping a `printf()` and a macro.
- tests: stop setting `CURL_GETHOSTNAME` where unnecessary.

Closes #14695

tests/data/test933

@@ -34,18 +34,9 @@ SSL
 <name>
 SMTP NTLM graceful cancellation
 </name>
- <setenv>
-# we force our own host name, in order to make the test machine independent
-CURL_GETHOSTNAME=curlhost
-# we try to use the LD_PRELOAD hack, if not a debug build
-LD_PRELOAD=%PWD/libtest/.libs/libhostname.so
- </setenv>
 <command>
 smtp://%HOSTIP:%SMTPPORT/%TESTNUMBER --mail-rcpt recipient@example.com --mail-from sender@example.com -u testuser:testpass -T -
 </command>
-<precheck>
-chkhostname curlhost
-</precheck>
 </client>
 
 #