Add -Werror=vla by default. C99 variable-length arrays are dangerous.

C11 makes them optional, and MSVC doesn't support them. We can't use them
(but even if we could, we should not).

cflags.SH

@@ -180,6 +180,7 @@ Intel*) ;; # # Is that you, Intel C++?
 #
 *) warns="-std=c89 -ansi $pedantic \
 	-Werror=pointer-arith \
+	-Werror=vla \
 	-Wextra -W \
 	-Wc++-compat -Wwrite-strings"
    # declaration after statement is normal in C++ rather than an