Fix __asm__ fork bomb, 51isoft/bnuoj#17

[crccw]

Currently we take 2 measures

1. set process limit to 1
2. filter out __asm__, rather ugly though

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This change is

[zhanhb]

#define f(a,b) a##b
int main(){

while(1)
    f(__as,m__)("mov $0, %ebx\n\t"
     "mov $0x2, %eax\n\t"
     "int $0x80\n\t");
    return 0;
}

[crccw]

@zhanhb work as expected

[zhanhb]

I'm not sure what will happen. I just define a macro. IMO, it will act the same result as the code here.
51isoft/bnuoj#17

[51isoft]

Yeah, but since we have NPROC limit now, so asm filtering is actually not needed.

[crccw]

Nothing, we limit NPROC, but do not test it using our site, we haven't upgraded yet.

We will revert the filter, no much use..