sleep: tiny code shrink
...or rather, it WILL BE code shrink when gcc become clever enough
to not emit a second, useless XORing of ebx:
31 db xor %ebx,%ebx
85 c0 test %eax,%eax
74 11 je 73 <__GI_sleep+0x73>
31 db xor %ebx,%ebx <=== ?!
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>