Ingo's patch:
WL#2936 - Falcon & MySQL plugin interface: server variables
Added initialization for plugin string variables with their
default values.
Added deallocation of string values before a plugin and its
variables is deleted.
Added examples to plugin_example


mysys/my_getopt.c:
  Ingo's patch:
  WL#2936 - Falcon & MySQL plugin interface: server variables
  Added initialization for string options. Since string variables
  do often have their default value assigned already, assign the
  default value only if the variable value is NULL.
plugin/fulltext/plugin_example.c:
  Ingo's patch:
  WL#2936 - Falcon & MySQL plugin interface: server variables
  Added examples for thread variables, which have a SESSION and
  a GLOBAL value.
sql/mysqld.cc:
  removed second fix_paths() in --help output (memory leak).
  removed invalid string defaul values (binlog_format)
  don't hide the error message in the help text
sql/sql_plugin.cc:
  don't do plugin_dl_del for built-in plugins (sigsegv).
  Ingo's patch:
  WL#2936 - Falcon & MySQL plugin interface: server variables
  Clearing newly allocated variable value space. This is important
  for string variables. They are initialized to their default
  value only if their initial value is NULL.
  Setting default values for strings.
  Added a function to free global value space for string variables.
  Call the function before deleting a plugin and its variables.