common BUFSIZ BSS buffer, small reduce code, data and bss

include/libbb.h

@@ -333,6 +333,12 @@ extern const char * const bb_path_group_file;
 extern const char * const bb_path_securetty_file;
 extern const char * const bb_path_motd_file;
 extern const char * const bb_dev_null;
+
+#ifndef BUFSIZ
+#define BUFSIZ 4096
+#endif
+extern char bb_common_bufsiz1[BUFSIZ+1];
+
 /*
  * You can change LIBBB_DEFAULT_LOGIN_SHELL, but don`t use,
  * use bb_default_login_shell and next defines,