* builtins.c, calls.c: Change all instances of gen_call_* or
gen_sibcall_* to GEN_CALL_* and GEN_SIBCALL_*.
* calls.c (struct_value_size_rtx): Separate definition from
initialization to avoid unused variable warning.
* genflags.c (gen_macro): New function.
(gen_proto): Call it for gen_call_* and gen_sibcall_*.
(gen_nonproto): Delete.
(gen_insn): Put all insns on the same obstack.
(main): Generate prototypes for everything unconditionally.