Merge branch 'fix_ub_shift' of https://github.com/wojdyr/stb into working

tests/test_sprintf.c

@@ -85,6 +85,7 @@ int main()
    CHECK2("0.00", "%.2f", 1e-4);
    CHECK2("-5.20", "%+4.2f", -5.2);
    CHECK2("0.0       ", "%-10.1f", 0.);
+   CHECK2("-0.000000", "%f", -0.);
    CHECK2("0.000001", "%f", 9.09834e-07);
 #if USE_STB  // rounding differences
    CHECK2("38685626227668133600000000.0", "%.1f", pow_2_85);