string manipulation : removing a part of a string

[Vincent Torri]

Hey

I pass -Wno-foo as a parameter of an m4 macro. What I would like is to 
store into a variable -Wfoo, so removing 'no-'

Is it possible with the m4 macro string manipulation ? If not, what's the 
best solution ?

Another related question: if I pass -Wbar, I would like to know if it 
begins by '-Wno-'. How can I do that with m4 ?

thank you

Vincent Torri