Fix #370 - Some memory leaks

Fix memory leak in r_config_new.
  cfg->nodes->free should be a custom function that frees RConfigNode
  structure correctly, but not the ordinary free.
Fix memory leak in r_anal_new.
  In r_anal_free need to call r_meta_free to free the
  whole RMeta structure, not only it's data list.
  The r_meta_free doesn't seem to have any leak itself.
Fix leaking anal->hints.
Fix memory leaks in r_cmd_free
Fix memory leak in r_cmd_plugin_init
Fix memleak in r_lib_new
Fix memory leak in r_io_plugin_init
Fix memory leak in r_debug_trace_new
Fix memory leaks in r_io_new
Fix memory leak in r_graph_new
Fix memory leak in r_sys_getdir.
  Note: calling getcwd with dir=NULL is a Linux-specific extension
  of POSIX, not sure if works on other non-windows platforms.
Fixes a typo