RFC: should we use -Werror? (& sample patch to do it)

[Dan Nicolaescu]

What about changing -Werror to be a little bit more fine grained: so
it would be possible to specify exactly  which warnings would be
errors. 

Something like -Werror=LIST_OF_WARNINGS_THAT_SHOULD_GENERATE_ERRORS
or -WWARNING_NAME=error

Then we could turn on -Werror for all the un-controversial warnings,
that don't generate false positives, like -Wformat,
-Wstrict-prototypes, etc. 

(currently we have fine grained control for warnings, but not for 
-Werror). 

Just my 2 cents

        --dan