bring speed back into KConfig

[Juergen Pfennig]

Beware!

Hi, long ago I had a deep look at the kde3 code because it caused a crash.

> > The code now uses highlevel QByteArray operations and even worse QFile
> > operations for operating on the .ini files.

I also found (at that time) that the code was not perfectly optimized and it 
was not capable of handling different line ending styles CR vs LF vs CR LF 
and it did not handle various unicode encodings correctly.

> I.e. for parsing the ini-style rc files ?
> Uh, this code was _really_ optimized before.

Again: the use of mmap() caused exceptions in one network filesystem (smb at 
that time). Please be very carefull before changing it.

Yours Jürgen