Fixed includes and a couple of other things in STLport, now on to compiling and linking helloworld:
make: Entering directory `/data/nios/nios2-linux/uClinux-dist/user/cxxtest/helloworld'
nios2-linux-uclibc-g++ -L/data/nios/nios2-linux/uClinux-dist/lib/STLport/lib -o cxx_helloworld helloworld.o -lm -Wl,-Bstatic -lstdc++ -Wl,-Bdynamic
helloworld.o(.text+0x20): In function `std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
: undefined reference to `std::basic_string<char, std::char_traits<char>, std::allocator<char> >::size() const'
helloworld.o(.text+0x80): In function `std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
: undefined reference to `std::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator(unsigned long) const'
helloworld.o(.text+0xdc): In function `std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
: undefined reference to `std::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator(unsigned long) const'
helloworld.o(.text+0x114): In function `std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
: undefined reference to `std::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator(unsigned long) const'
helloworld.o(.text+0x188): In function `main':
: undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)'
/data/nios/nios2-linux/uClinux-dist/lib/STLport/lib/libstdc++.a(iostream.o)(.text+0x3b8): In function `std::_Stl_create_wfilebuf(__STDIO_FILE_STRUCT*, int)':
: undefined reference to `__gxx_personality_sj0'
and so on...