Why do we keep UnusedLock1 in LWLockId?

Hi,

There is UnusedLock1 in LWLockId enumerations in storage/lwlock.h .
|    UnusedLock1,                /* FreeSpaceMapLock used to be here */

I thought it is for keeping LWLockId same as 8.3 at first,
but we've already split SInvalLock to SInvalReadLock and
SInvalWriteLock. So the IDs are changed anyway.

Are there any reason to keep UnusedLock1 there?
Or can we remove it simpley?

Regards,
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ITAGAKI Takahiro
NTT Open Source Software Center