NTLM tests: boost coverage by forcing the hostname

A shared library tests/libtest/.libs/lihostname.so is preloaded in NTLM
test-cases to override the system implementation of gethostname().  It
makes it possible to test the NTLM authentication for exact match, and
this way test the implementation of MD4 and DES.

If LD_PRELOAD doesn't work, a debug build willl also workk as debug
builds are now made to prefer a specific environment variable and will
then return that content as host name instead of the actual one.

Kamil wrote the bulk of this, Daniel Stenberg polished it.

tests/data/test239

@@ -56,9 +56,18 @@ NTLM
  <name>
 HTTP proxy-auth NTLM and then POST
  </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=./libtest/.libs/libhostname.so
+ </setenv>
  <command>
 http://%HOSTIP:%HTTPPORT/239 --proxy http://%HOSTIP:%HTTPPORT --proxy-user silly:person --proxy-ntlm -d "postit"
 </command>
+<precheck>
+chkhostname curlhost
+</precheck>
 </client>
 
 # Verify data after the test has been "shot"
@@ -66,11 +75,6 @@ http://%HOSTIP:%HTTPPORT/239 --proxy http://%HOSTIP:%HTTPPORT --proxy-user silly
 <strip>
 ^User-Agent: curl/.*
 </strip>
-# We strip off a large chunk of the type-2 NTLM message since it depends on
-# the local host name and thus differs on different machines!
-<strippart>
-s/^(Proxy-Authorization: NTLM TlRMTVNTUAADAAAAGAAYAEAAAAAYABgAWAAAAAAAAABwAAAABQAFAHAAAAA).*/$1/
-</strippart>
 <protocol nonewline="yes">
 POST http://%HOSTIP:%HTTPPORT/239 HTTP/1.1
 Proxy-Authorization: NTLM TlRMTVNTUAABAAAABoIIAAAAAAAAAAAAAAAAAAAAAAA=
@@ -82,7 +86,7 @@ Content-Length: 0
 Content-Type: application/x-www-form-urlencoded
 
 POST http://%HOSTIP:%HTTPPORT/239 HTTP/1.1
-Proxy-Authorization: NTLM TlRMTVNTUAADAAAAGAAYAEAAAAAYABgAWAAAAAAAAABwAAAABQAFAHAAAAA
+Proxy-Authorization: NTLM TlRMTVNTUAADAAAAGAAYAEAAAAAYABgAWAAAAAAAAABwAAAABQAFAHAAAAAIAAgAdQAAAAAAAAAAAAAABoKBAKAeQjzKtCQ7ubW8S6MN7B59436GAxPu0CVROwwNBsgxML49gcbAXLT/bU+H5wrS9XNpbGx5Y3VybGhvc3Q=
 User-Agent: curl/7.13.2-CVS (i686-pc-linux-gnu) libcurl/7.13.2-CVS OpenSSL/0.9.7e zlib/1.2.2 libidn/0.5.13
 Host: %HOSTIP:%HTTPPORT
 Accept: */*