Provide a function to set 'hostname' field in log

test/test-cases/regression/fn-setHostname.json

@@ -0,0 +1,41 @@
+[
+  {
+    "enabled":1,
+    "version_min":300000,
+    "title":"Testing function :: setRequestHostName",
+    "client": {
+      "ip":"200.249.12.31"
+    },
+    "server":{
+      "ip":"200.249.12.31",
+      "port":80,
+      "hostname":"modsecurity.org"
+    },
+    "request": {
+      "headers": {
+        "Host":"www.modsecurity.org"
+      },
+      "uri":"/foo?q=attack",
+      "http_version": 1.1
+    },
+    "response":{
+      "headers":{
+        "Date":"Mon, 13 Jul 2015 20:02:41 GMT",
+        "Last-Modified":"Sun, 26 Oct 2014 22:33:37 GMT",
+        "Content-Type":"text/plain"
+      },
+      "body":[
+        "denystring"
+      ]
+    },
+    "expected":{
+      "http_code": 200,
+      "debug_log": "[hostname: \"modsecurity.org\"]"
+    },
+    "rules":[
+      "SecRuleEngine On",
+      "SecResponseBodyAccess On",
+      "SecRule ARGS_GET \"@contains attack\" \"id:1,phase:2,deny\""
+    ]
+  }
+]