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.

memheap: check against over written in rt_memheap_free

bsp/{cortex-M}: fix the SysTick_Config

vbus: remove the rt_ prefix in the watermark queue source file

SysTick_Config substract one inside the function. So there is no need to
substract one when passing the parameter.

Lpc43xx

SCons will omit the file in parent dir of SConstruct somehow and build
the object files in that dir instead of in variant dir. This cause
problem because we cannot mix the object files between M0 and M4 which
SCons failed to rebuild. So we have to manually remove the files before
building.

Currently only lpc43xx is supported.