Don't remove mnemonics and parentheses under non-Mac system.

SHA: 8e3aacf61b is a mac only patch, but
some code introduced by which is not wrapped with Q_OS_MAC. So add
the missing Q_OS_MAC here.

Change-Id: I748d46b977740e6116dab5659ad1e47d23262a0f
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>

src/gui/painting/qpainter.cpp

@@ -7462,6 +7462,7 @@ start_lengthVariant:
                     range.format.setFontUnderline(true);
                     underlineFormats.append(range);
                 }
+#ifdef Q_OS_MAC
             } else if (hidemnmemonic && *cin == QLatin1Char('(') && l >= 4 &&
                        cin[1] == QLatin1Char('&') && cin[2] != QLatin1Char('&') &&
                        cin[3] == QLatin1Char(')')) {
@@ -7473,6 +7474,7 @@ start_lengthVariant:
                 length -= n + 4;
                 l -= 4;
                 continue;
+#endif //Q_OS_MAC
             }
             *cout = *cin;
             ++cout;