C++ exception support

[Christoph Feck]

Hi,

with the recent merge of S60 stuff into Qt 4.6 master, Qt gets more picky 
about C++ exceptions. While it is no problem to continue building KDE without 
exceptions (KDE uses -fno-exceptions) while Qt was built with exceptions 
(which is the default behaviour), it will be required to inform Qt about it 
when including headers with Qt 4.6.

A special "-DQT_NO_EXCEPTIONS" needs to be defined when you disable 
exceptions, according to Thiago. Without this flag, KDE fails to compile. 
Setting this define should have also been done for Qt 4.5, but since KDE does 
not use the QtXmlPatterns module, this was not a problem before.

I already committed r1015193 for kdesupport, but I am sure the fix in other 
modules isn't that simple because of the KDE4_ENABLE_EXCEPTIONS define, which 
would have to both set "-fexceptions", as well as undefine any 
previous "-DQT_NOEXCEPTIONS".

Maybe there should be a new kde4_enable_exceptions() cmake macro that does the 
work, instead of using the simple define, but I leave that (and the actual 
work to implement that macro) to buildsystem experts.

Thanks,
Christoph Feck (kdepepo)
(not subscribed to kde-buildsystem)

References:
http://websvn.kde.org/?view=rev&revision=1015193