More build fixes.
Changed the documentation builder to automatically prepend %EPOCROOT% (converted to a path relative form) to pre-processor include path options that start with 'epoc32'. Prevously $(EPOCROOT) was prepended in the makefile, which broke the documentation build because the pre-processor will only accecpt relative path include options.
Fixed a defect in iosrv.exe that caused a panic if a foreground read object was attached to a different end point.
This was due to the read object being notified of a change in foreground before its iEndPoint member was updated. This member is now updated before attempting the attach, and is set to NULL in the event of a leave (resulting in the read object being left in an unattached state).
Also tweaked ymodem.cif to make it more readable.