[C] Fix mismatched '// CraftBukkit' comments

Fixes a few '// CraftBukkit start'.. '//CraftBukkit end' comments, per https://github.com/Bukkit/CraftBukkit/blob/master/README.md

* Mark your changes with:
    * 1 line; add a trailing: `// CraftBukkit [- Optional reason]`
    * 2+ lines; add
        * Before: `// CraftBukkit start [- Optional comment]`
        * After: `// CraftBukkit end`

No functional changes; cosmetic only

Leaky ticket: none yet