Merge branch '1845_code_cleanup'

Merge branch '1845_code_cleanup'

* 1845_code_cleanup: (30 commits)
  editcmd.c 'eval_marks': removed unused variable 'diff'
  The check result of g_new(), g_new0(), g_malloc(), g_malloc0() and g_realloc() is useless.
  Remove declaration of unused function.
  Added glib library for mcserv
  rearranging some lines in src_skin_colors.c mc_skin_color_parse_ini_file()
  missing check in src_mcconfig_get.c-mc_config_get_groups()_-2
  Unifying of g_strconcat() calls
  Types accuracy, minor optimization, removed unneeded goto and return.
  Fixed i18n of file operation dialog titles.
  added NULL check before call g_utf8_find_prev_char, g_utf8_get_char_validated for more safety.
  More usage of GLib functions.
  No need to call done_menu() at MC exit.
  Optimization of DLG_RESIZE message handling.
  doxygen: various warning fixes
  Fixed forgotten call of va_end() in mc_log().
  src/boxes.c (configure_vfs): fixed #ifdef directive.
  m4.include/mc-cflags.m4: added -fdiagnostics-show-option (exact warning option)
  configure.ac: guard $CFLAGS with "" in tests
  m4.include/mc-cflags.m4: sorted CFLAGS (no flags were added or removed)
  cflags: enable -Wformat in maintainer mode
  ...