Windows(tm) CreateProcess does not use the env passed to it to find the
executables. So we have to modify our own PATH to make Popen work. Also,
detect the cmd build-in commands and execute it directly.

Tested on MDK toolchain on RB4088 and the MSVS toolchain on simulator
BSP.

Update SConscript

Update stm32_rom.ld

Update rtconfig.py

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.