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.
These two executables exists to allow fshell to eclipse the ROM based "econs.dll". This can't be done
within the .SIS file because the app installer doesn't allow ROM files to be eclipsed.
fshell_inst.exe copies "<install_drive>:\sys\bin\iocons.dll" to "<install_drive>:\sys\bin\econs.dll".
It is launched by the tool-kit .SIS file at install time.
fshell_uinst.exe deletes "<install_drive>:\sys\bin\econs.dll".
It is launched by the tool-kit .SIS file at uninstall time.