Warn when assigning to a function pointer with an unmatching
signature. This usually happens in cases like assigning the null
function to an entity's .think function pointer.
-.It Fl W Ns Cm preprocessor
-Enable warnings coming from the preprocessor. Like duplicate macro
-declarations. This warning triggers when there's a problem with the
-way the preprocessor has been used, it will \fBnot\fR affect warnings
-generated with the '#warning' directive. See -Wcpp.
.It Fl W Ns Cm cpp
Show warnings created using the preprocessor's '#warning' directive.
.It Fl W Ns Cm multifile-if