post-review fixes + cleanup + some minor fixes

server-tools/instance-manager/buffer.cc:
  coding style fixes
server-tools/instance-manager/buffer.h:
  wrong constructor initialisation fixed
server-tools/instance-manager/commands.cc:
  cleanup
server-tools/instance-manager/guardian.cc:
  cleanup + added lock/unlock routines
server-tools/instance-manager/guardian.h:
  GUARD_NODE moved to the header
server-tools/instance-manager/instance.cc:
  Fix for the linuxthreads/POSIX signal handling problem (see comments in the code)
server-tools/instance-manager/instance.h:
  condition variable renamed and commented
server-tools/instance-manager/instance_map.cc:
  We need to refresh guardian during flush_instances
server-tools/instance-manager/instance_map.h:
  removed obsolete function declaration
server-tools/instance-manager/instance_options.cc:
  added caching of computed values
server-tools/instance-manager/instance_options.h:
  added vars to cache some option values
server-tools/instance-manager/listener.cc:
  check whether we are running on the linux threads
server-tools/instance-manager/manager.cc:
  lock guardian before init()
server-tools/instance-manager/parse_output.cc:
  cleanup
server-tools/instance-manager/priv.cc:
  added global variables to detect whether we are running on the LinuxThreads
server-tools/instance-manager/priv.h:
  added global variables to detect whether we are running on the LinuxThreads

server-tools/instance-manager/buffer.h

@@ -41,7 +41,7 @@ private:
   int error;
 public:
   Buffer(size_t buffer_size_arg= BUFFER_INITIAL_SIZE)
-    :buffer_size(BUFFER_INITIAL_SIZE), error(0)
+    :buffer_size(buffer_size_arg), error(0)
   {
     /*
       As append() will invokes realloc() anyway, it's ok if malloc returns 0