In thread context means: 1) the scheduler has been started; 2) not in
interrupt context. It is more stronger than RT_DEBUG_NOT_IN_INTERRUPT.
With this commit, you will catch the error on situations like taking
mutex before scheduling instead of crashing on NULL pointer reference.

components/utilities: add ymodem

Real-YModem implemented a flexible YModem support. It use callback-based
structure to let the user application to deal with the data. It contains
3 examples:

    1. echo.c: write the data recieved on YModem to an other device
    2. null.c: discard the YModem data
    3. tofile.c: write the data to the file system

Currently, it does not support batch file transmission.

scons script: support to generate vs2012 project xml

rename template.vcproj to template_vs2005.vcproj
add template_vs2012.vcxproj
NOTE: the vs2012.py is ugly, just can work.

DFS/jffs2: fix file mode init bug in jffs2_open/opendir

found by haitao5198
clear mount parition device talbe when jffs2 mount falied

found by haitao52198
URL:http://www.rt-thread.org/phpBB3/viewtopic.php?f=3&t=3112&p=17153#p17153

Compiling fix

logtrace: cleanup code and fix compiling warnings

logtrace only use odd number of log levels. So the use could set some
custom level amount them.

kservice: export vsnprintf as rt_vsnprintf

vsnprintf is a common string function that could be used in many places.
Using both vsnprintf in libc and vsnprintf in the RTT could make a
bigger image. Moreover, if newlib is not enabled when compiling with
GCC, referencing vsnprintf will lead to link error:

    .../arm-none-eabi/lib/armv7-ar/thumb/softfp/libc.a(lib_a-sbrkr.o):
    In function `_sbrk_r':
    sbrkr.c:(.text._sbrk_r+0xc): undefined reference to `_sbrk'
    collect2: error: ld returned 1 exit status

Using rt_vsnprintf could avoid such problem.

finsh: unregister rx_indicate when closing the device

Because the device could still remain opened when closed by finsh, the
old rx_indicate is useless for finsh. Some buggy driver will still
generate rx_indicate even after the device has been closed. So FinSh
should unregister the rx_indicate when releasing the old device.

rt_event_recv: add a check on the option flag

Simulator

Either RT_EVENT_FLAG_AND or RT_EVENT_FLAG_OR should be set in the option
flag. If none of them is present, the waiting thread will never be
resumed.

This gives ways for bsp to set it's own RTT_CC.

Building is only the first step. Correctness is what we need. There are
already many GCC builds for other bsp so GCC building for simulator is
not important. So I use clang-analyze to check all the source codes in
simulator project. Hope it will help us.

When CROSS_TOOL or 'RTT_CC' env is setted to 'clang-analyze', it will
use Clang to check the codes.

Bsps can use the clang analyzer as a tool:

    env = Environment(toolpath=[os.path.join(RTT_ROOT, 'tools',
                      'tools')], tools = ['clang-analyze'])

When building the project, the static analyzer will be called to check
all the C code. The warnings are print to stderr.