HPHP: add mechanism to add hooks around server start.

Add mechanism to add hook around server start. Similar to the existing
Thread/Process Init/Fini hooks. This allows us to add behaviors around the main
hphp server start/stop event without introducing source code level dependency.

hphp/runtime/base/program_functions.cpp

@@ -76,8 +76,9 @@ extern char **environ;
 namespace HPHP {
 
 extern InitFiniNode *extra_process_init, *extra_process_exit;
+extern InitFiniNode *extra_server_init, *extra_server_exit;
 
- void initialize_repo();
+void initialize_repo();
 
 /*
  * XXX: VM process initialization is handled through a function
@@ -680,7 +681,13 @@ static int start_server(const std::string &username) {
     }
   }
 
+  for (InitFiniNode *in = extra_server_init; in; in = in->next) {
+    in->func();
+  }
   HttpServer::Server->run();
+  for (InitFiniNode *in = extra_server_exit; in; in = in->next) {
+    in->func();
+  }
   return 0;
 }
 

hphp/runtime/base/thread_init_fini.cpp

@@ -35,13 +35,15 @@ namespace HPHP {
 ///////////////////////////////////////////////////////////////////////////////
 
 InitFiniNode *extra_init, *extra_fini, *extra_process_init, *extra_process_exit;
+InitFiniNode *extra_server_init, *extra_server_exit;
 
 InitFiniNode::InitFiniNode(void(*f)(), When init) {
   InitFiniNode *&ifn =
     init == When::ThreadInit ? extra_init :
     init == When::ThreadFini ? extra_fini :
-    init == When::ProcessInit ? extra_process_init : extra_process_exit;
-
+    init == When::ProcessInit ? extra_process_init :
+    init == When::ProcessExit ? extra_process_exit :
+    init == When::ServerInit ? extra_server_init : extra_server_exit;
   func = f;
   next = ifn;
   ifn = this;

hphp/runtime/base/thread_init_fini.h

@@ -32,7 +32,9 @@ struct InitFiniNode {
     ThreadInit,
     ThreadFini,
     ProcessInit,
-    ProcessExit
+    ProcessExit,
+    ServerInit,
+    ServerExit
   };
   InitFiniNode(void(*f)(), When when);
   void (*func)();