add keil fpu support and gcc fpu support in scons building

Pulls

[bsp/stm32f40x] code style change

[bsp/lpc176x] Update emac.c

Fix PHY chip(dp83848c) init failed without Active Network.

TAB to 4 space

[bsp/stm32f40x] fix the uart3

[mempool] reset the thread->error before suspending thread

Time out result and other errors is recorded in thread->error. Dirty
error will screw up the error handling code after the thread has been
wake up.

[bsp/taihu] fix the link error

The taihu.lds hardcoded the path of start_gcc.o. Change it as the layout
of build/ has change by commit a03816ef.

Misc fix

The ptr is set in the following code. So remove the first one.

The digit in octal numbers should with in 0~7. Check on it in
token_proc_number. This issue is found by Clang.

Clang complains about "Null pointer argument in call to string
comparison function". So assert on it.

Fix some "unused variable" and "used before set" warnings.

Fix scons

Logtrace next

log_session_lvl is suitable for performance critical places where in
most cases, the log is turned off by level. If the session is const and
the level is greater than session->lvl, the whole function will be
optimized out.

Compiler may do more optimization when the parameter is const.

[USB]fix rt_usbd_set_config() BUG which set the USB device to configurat...

In SCons manual:

=================
In order to inform the C compiler about the repositories,  SCons will
add appropriate -I flags to the compilation commands for each directory
in the $CPPPATH list. So if we add the current directory to the
construction environment $CPPPATH like so:

    env = Environment(CPPPATH = ['.'])
    env.Program('hello.c')
    Repository('/usr/repository1')

Then re-executing SCons yields:

    % scons -Q
    cc -o hello.o -c -I. -I/usr/repository1 hello.c
    cc -o hello hello.o
=================

The additional include directory is definitely not what we want. Just
remove the additional Repository line.

BSPs could have their own components/ etc. If they point to the same
folder, SCons would find the wrong source code to compile.

update MSH ifconfig and add MSH netstat.