* genattrtab.c: Make generated file use system.h, instead of
        including stdio.h, etc directly.
        * genextract.c, genopinit.c, genoutput.c: Likewise.
        * genpeep.c, genrecog.c: Likewise
        * genoutput.c (process_template): Mark operands in the generated
        function as potentially unused if compiling with GNU CC.

From-SVN: r18941