Really fix airport_up_time

[usr-sse2]

0x10624DD3LL is just a constant used for optimized division by 1000: http://flaviojslab.blogspot.com/2008/02/integer-division.html
There is no need to write it in code, because the compiler does constant division optimization by itself.
Here is the assembly code that I get after compiling my variant:

__ZL15airport_up_timev:
00000000000149e0        pushq   %rbp
00000000000149e1        movq    %rsp, %rbp
00000000000149e4        subq    $0x20, %rsp
00000000000149e8        leaq    -0x10(%rbp), %rdi
00000000000149ec        xorl    %esi, %esi
00000000000149ee        movl    $0x10, %edx
00000000000149f3        callq   _memset
00000000000149f8        movq    $0x0, -0x18(%rbp)
0000000000014a00        leaq    -0x10(%rbp), %rdi
0000000000014a04        callq   _microuptime
0000000000014a09        imull   $0x10624dd3, -0x8(%rbp), %eax   ## imm = 0x10624DD3
0000000000014a10        movl    %eax, %eax
0000000000014a12        movq    %rax, -0x18(%rbp)
0000000000014a16        movq    -0x18(%rbp), %rax
0000000000014a1a        shrq    $0x3f, %rax
0000000000014a1e        movq    -0x18(%rbp), %rcx
0000000000014a22        shrq    $0x26, %rcx
0000000000014a26        addq    %rcx, %rax
0000000000014a29        imulq   $0x3e8, -0x10(%rbp), %rcx       ## imm = 0x3E8
0000000000014a31        addq    %rcx, %rax
0000000000014a34        addq    $0x20, %rsp
0000000000014a38        popq    %rbp
0000000000014a39        retq
0000000000014a3a        nopw    (%rax,%rax)

[zxystd]

It should be what I have misunderstood, thank you.