C++ support

Hi,

There is a problem. I changed main.c to main.cpp and also fixed build. It works fine but after adding line “std::string s;” I see a compiler error:

int main(void)
{
    std::string s;
e/c++/6.4.1/string:43,
                 from main.cpp:40:
skipped/asdk/ambd_sdk/project/realtek_amebaD_va0_example/GCC-RELEASE/xml/toolchain/linux/asdk-6.4.1/linux/newlib/arm-none-eabi/include/ctype.h:14:4: error: expected unqualified-id before 'int'
 int _EXFUN(isalpha, (int __c));
    ^~~
skipped/asdk/ambd_sdk/project/realtek_amebaD_va0_example/GCC-RELEASE/xml/toolchain/linux/asdk-6.4.1/linux/newlib/arm-none-eabi/include/ctype.h:14:4: error: expected ')' before 'int'

What is missing?

macros in the following file: component/soc/realtek/amebad/swlib/string/strproc.h
are messing with the cpp headers.
easiest solutions is to comment them out.