I grabbed a fresh testing copy of LSL5, decompiled all, and did a "Find in Files" (Ctrl-Shift-F) for "to move your". The line helpStr {Use this icon to move your character.} was right there.
There were some mild incompatibilities like proc0_25 (aka CenterDisplay) having a (Display &rest dsALIGN 1 ... ) in it, which is forbidden by the compiler but easily resolved by slipping in a third named argument. Just that and one other slip-up and it compiled.
The bigger problem is that it wouldn't pack properly. Somehow it seemed to mistakenly build a resource.000 where it should've used resource.001, like an SCI 1.0 game would expect. And let me tell you, I am pissed as hell about that.