Для:
Bigchel пришла в голову мысль - а для Borland C++ 3.1 есть реализация stl? Да вроде там её никогда не было

Меняй компилятор на
Цитата(http://www.sgi.com/tech/stl/)
The STL was developed on SGI MIPSproTM C++ 7.0, 7.1, 7.2, and 7.2.1. If you are using the 7.0 compiler, you must compile using either the -n32 or the -64 flag; if you are using 7.1 or later, you may use -o32, -n32, or -64. The STL has also been tested on Microsoft Visual C++ 5.0, on g++ 2.8.1, and on recent egcs snapshots. All of the STL except for the <string>, <bitset>, and <valarray> headers has also been tested on Borland 5.02.
или ищи порт под Borland C++ 3.1