To avoid same file name, therefore change the netdb.c to lwip_netdbc in
dfs_lwip.

The old `--keep` parameter for Keil is wrong. RTFM of Keil and get it
right.

Remove dataqueue/pipe if not enable RT_USING_HEAP, supply the missing `not`.

fix: completion wait after, maybe can't clean the flag.

[BSP] Correct pin register name problems

format. It is targeted at 32 bit microcontrollers, but is also fit for
other embedded systems with tight (2-10 kB ROM, <1 kB RAM) memory
constraints.(http://koti.kapsi.fi/jpa/nanopb/)

How to use the example:
	1. move examples/nanopb to bsp/xxxx/
	2. enable macro RT_USING_NANOPB in rtconfig.h
	3. regenerate the project file (scons --target=xxxx)
	4. rebuild the project

[Driver/ringbuffer]: Fix put_force bug

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.

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.

Currently only lpc43xx is supported.

Misc fix

As we are sending C continuously, there is a chance that the
sender(remote) receive an C after sending the first handshake package.
So the sender will interpret it as NAK and re-send the package. So we
just ignore it and proceed.

This saves 1KiB ram usage.

There is no list_mem and only list_memheap when RT_USING_MEMHEAP_AS_HEAP
is enabled.

System will crash when the romfs is erased. Add checks before using them
to avoid it.

sync

Move PNG_NO_WRITE_SUPPORTED outside of RT_USING_NEWLIB. #197

Frequent 'C' on the handshake will confuse some sender(lrzsz for
example).

Make fast path fast and slow path slow.

2. Fix data transfer size calculate error issue;