handling of warnings

[skaller]

g++ 3.2.2 doesn't support -Wno-invalid-offsetof

when I use it I get an error:

g++ -Wno-invalid-offsetof -ansi -pedantic -shared -I.
tut/examples/tut115.cpp -o tut/examples/tut115.so
cc1plus: unrecognized option `-Wno-invalid-offsetof'
 
I think this behaviour is inappropriate. By default, if a warning
control option is not recognized it should be ignored, or a warning
produced. 

The reason for this suggestion is: when one creates a build script,
new options cannot easily be used, since with the existing behaviour
on an older version of the compiler, the compile fails .. when 
all we wanted was some control over warnings.

The current status is: my build script has to use -w
to remove an unwanted warning. I can't change that to a new
explicit flag, even if I get a newer version of gcc,
because my clients may not have it.