Commit 0512ea8d65 changed the value of the tracker_ upid codes when
they were converted from `#define` statements with explicit values to
`enum` members with implicit values. The tracker program is maintained
separately, and continues to use the old values, so games with this
commit use the wrong numbers when requesting service from the tracker.
Switch the upid codes back to their previous values, and add a warning
comment about the special compatibility concerns for tracker upid
codes, relative to game-to-game codes.
Fixes: 0512ea8d65 ("Use enum class for upid")
b8cc509cbe