silence gcc warnings: missing prototypes and unused variables

R=ken
OCL=19583
CL=19583

src/cmd/6g/gen.c

@@ -6,6 +6,7 @@
 #undef	EXTERN
 #define	EXTERN
 #include "gg.h"
+#include "opt.h"
 
 enum
 {
@@ -515,7 +516,7 @@ swgen(Node *n)
 	Case *s0, *se, *s, *sa;
 	Prog *p1, *dflt;
 	int32 lno;
-	int any, nc, w;
+	int any, nc;
 	Iter save1, save2;
 
 // botch - put most of this code in

src/cmd/6g/opt.h

@@ -149,6 +149,7 @@ Bits	blsh(uint);
 int	beq(Bits, Bits);
 int	bset(Bits, uint);
 int	Qconv(Fmt *fp);
+int	bitno(int32);
 
 /*
  * reg.c

src/cmd/6g/reg.c

@@ -36,7 +36,7 @@
 #define	P2R(p)	(Reg*)(p->reg)
 #define	MAGIC	0xb00fbabe
 
-static	first	= 1;
+static	int	first	= 1;
 static	void	dumpit(char *str, Reg *r0);
 static	int	noreturn(Prog *p);
 
@@ -73,8 +73,8 @@ rcmp(const void *a1, const void *a2)
 void
 regopt(Prog *firstp)
 {
-	Reg *r, *r1, *r2;
-	Prog *p1, *p;
+	Reg *r, *r1;
+	Prog *p;
 	int i, z, nr;
 	uint32 vreg;
 	Bits bit;