Oops, that wasn't my comment to change.
Moved RowMarkRequiresRowShareLock next to the relevant enum.
Removed stray curly braces
Use assignment to convert between enums.  Compile time assertions about values and ordering.
Merged the 3 enumerations into 1 under utils, as suggested by Tom Lane
Renamed skip-locked-data.(spec|out) to skip-locked.(spec|out).