Added explicit calls to fstream::close rather than relying on destructors as a tentative gcc-cygwin fix.

[SVN r21287]

example/snippets/partial_regex_grep.cpp

@@ -79,6 +79,7 @@ int main(int argc, char* argv[])
          std::ifstream fs(argv[i]);
          if(fs.bad()) continue;
          search(fs);
+         fs.close();
       }
    }
    else