Qualify a file-defined IFCX path with the slot. IFCX paths may or may not
carry a leading slash; the result always has the form <prefix>/<rest> so
pathInSlot recognises it, and the original spelling is kept verbatim
after the prefix (a legacy slot returns the path unchanged).
Qualify a file-defined IFCX path with the slot. IFCX paths may or may not carry a leading slash; the result always has the form
<prefix>/<rest>sopathInSlotrecognises it, and the original spelling is kept verbatim after the prefix (a legacy slot returns the path unchanged).