Correct dfs fd_is_open search index error

[Driver/ringbuffer]: Fix put_force bug

[BSP] Add more features for STM32F4.

    OXape reports: http://www.rt-thread.org/phpBB3/topic3939.html
          driver/ringbuffer: when data length is bigger than space length
          for rb, the read_index in rb is not update.
    When length > space, update the read_index, the bug can be fix, and
          works fine.

crt_init: fix hardfault in Keil toolchain when there is no cpp object

If there is no SHT$$INIT_ARRAY, calling
$Super$$__cpp_initialize__aeabi_() will fault. At least until Keil5.12
the problem still exists. So we have to initialize the C++ runtime our
own.