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/parse_output.cc

@@ -53,7 +53,7 @@ int parse_output_and_get_value(const char *command, const char *word,
 
   wordlen= strlen(word);
 
-  if ((output= popen(command, "r")) == NULL)
+  if (!(output= popen(command, "r")))
     goto err;
 
   /*