htlc.h: move NUM_SIDES to define, not enum member

[niftynei]

Drive by fixup.

Changelog-None

[ZmnSCPxj]

I believe the intent here is that this is always the last entry in this enum, so that if we ever get more than two sides to a channel (fat chance), we just insert them before the NUM_SIDES entry. Standard C assigns enum values monotonically IIRC.

With NUM_SIDES as a #define you have to insert the new side to the enum, and update the #define.

But in any case there is going to be a lot more changes if we ever have more than two sides to a channel so....

[niftynei]

Using this comment as context for this change #4146 (comment)

[cdecker]

The rationale for not having it as part of the enum but rather have a #define is that exhaustive matching requires us to add a case NUM_SIDES to all switch statements (and technically if statements) if we keep it as part of the enum. +1 for moving it to a #define.

[cdecker]

ACK c824623

[cdecker]

The rationale for not having it as part of the enum but rather have a #define is that exhaustive matching requires us to add a case NUM_SIDES to all switch statements (and technically if statements) if we keep it as part of the enum. +1 for moving it to a #define.