this patch fixes inifinite loop in following testcase:

#include <fstream>
#include <string>
#include <cassert>
int main()
{
        std::ifstream in( "/tmp" );
        assert( in.good() );
        std::string buf;
        std::getline( in, buf );
        assert( in.fail() );
}

Index: STLport-trunk/stlport/stl/_fstream.c
===================================================================
--- STLport-trunk/stlport/stl/_fstream.c	(wersja 3579)
+++ STLport-trunk/stlport/stl/_fstream.c	(wersja 3580)
@@ -513,6 +513,12 @@
   // to make progress.
   for (;;) {
     ptrdiff_t __n = _M_base._M_read(_M_ext_buf_end, _M_ext_buf_EOS - _M_ext_buf_end);
+    if (__n < 0) {
+      // Read failed, maybe we should set err bit on associated stream...
+      this->setg(0, 0, 0);
+      return traits_type::eof();
+    }
+
     _M_ext_buf_end += __n;
 
     // If external buffer is empty there is nothing to do.