Auto merge of #813 - ndusart:syscall-android, r=alexcrichton

SYS_* constants are of type long in Android

The SYS_* constants should be `c_long` as `syscall` expect a `c_long` as first argument and in Android headers, there is no sign that these constants should be `unsigned long`.

So the compilation targeting ARM Android fails for dependent crates using `syscall`.