[patch] cleanup -Wmissing-variable-declarations warnings

[and]

fix -Wmissing-variable-declarations warnings and add to mc cflags

color-internal.c:57:28: warning: no previous extern declaration for non-static variable 'color_table' [-Wmissing-variable-declarations]
color-internal.c:84:28: warning: no previous extern declaration for non-static variable 'attributes_table' [-Wmissing-variable-declarations]
vfs.c:65:12: warning: no previous extern declaration for non-static variable 'vfsclasses_list' [-Wmissing-variable-declarations]
vfs.c:67:10: warning: no previous extern declaration for non-static variable 'vfs_str_buffer' [-Wmissing-variable-declarations]
vfs.c:68:19: warning: no previous extern declaration for non-static variable 'current_vfs' [-Wmissing-variable-declarations]
interface.c:67:16: warning: no previous extern declaration for non-static variable 'mc_readdir_result' [-Wmissing-variable-declarations]
boxes.c:96:15: warning: no previous extern declaration for non-static variable 'configure_old_esc_mode_id' [-Wmissing-variable-declarations]
boxes.c:96:42: warning: no previous extern declaration for non-static variable 'configure_time_out_id' [-Wmissing-variable-declarations]
boxes.c:114:12: warning: no previous extern declaration for non-static variable 'skin_names' [-Wmissing-variable-declarations]
boxes.c:115:8: warning: no previous extern declaration for non-static variable 'current_skin_name' [-Wmissing-variable-declarations]
filegui.c:253:3: warning: no previous extern declaration for non-static variable 'progress_buttons' [-Wmissing-variable-declarations]
find.c:195:14: warning: no previous extern declaration for non-static variable 'quit_button' [-Wmissing-variable-declarations]
layout.c:105:5: warning: no previous extern declaration for non-static variable 'ok_to_refresh' [-Wmissing-variable-declarations]
extfs.c:69:9: warning: no previous extern declaration for non-static variable 'extfs_plugins' [-Wmissing-variable-declarations]
args.c:50:10: warning: no previous extern declaration for non-static variable 'mc_argsshow_version' [-Wmissing-variable-declarations]
args.c:195:15: warning: no previous extern declaration for non-static variable 'terminal_group' [-Wmissing-variable-declarations]
args.c:282:15: warning: no previous extern declaration for non-static variable 'color_group' [-Wmissing-variable-declarations]
setup.c:127:5: warning: no previous extern declaration for non-static variable 'saving_setup' [-Wmissing-variable-declarations]

Signed-off-by: Andreas Mohr <and@…>

[andrew_b]

Thanks!
Applied as [f1b73ffe6e695d7477d45b0b103474b689a04474].