Issue 11788 - [x86] Valgrind unhandled instruction bytes: 0xC8 0x8 0x0 0x0

Use combination of PUSH, MOV and SUB instead of unsupported ENTER instruction, as recommended [here](https://bugs.kde.org/show_bug.cgi?id=88116).

Also, why the hell is this code generated manually? @WalterBright