Broken exception in Symbian, potentially will cause undefined behavior when receiving bad SIP message

[bennylp]

The exception framework for Symbian target relies on sources being compiled as C++, since the exception uses C++ exception. With Carbide, turns out the GCCE option "-x c++" DOES NOT work, and this will break the exception framework.

The exception framework is used heavily by the parser, to report syntax errors. Without this, syntax errors will go undetected, and possibly causes undefined behavior or even crashes.

This bug can be reproduced by running the exception test in pjlib-test.

In the MMP files, the compile as C++ option has been re-added to relevant libraries by ticket #887