runtime: fix plan9, windows builds

TBR=dvyukov
CC=golang-dev
https://golang.org/cl/10229043

src/pkg/runtime/os_plan9_386.c

@@ -95,7 +95,7 @@ Throw:
 	runtime·printf("\n");
 
 	if(runtime·gotraceback(&crash)) {
-		runtime·traceback((void*)ureg->pc, (void*)ureg->sp, 0, gp);
+		runtime·traceback(ureg->pc, ureg->sp, 0, gp);
 		runtime·tracebackothers(gp);
 		runtime·dumpregs(ureg);
 	}

src/pkg/runtime/os_plan9_amd64.c

@@ -103,7 +103,7 @@ Throw:
 	runtime·printf("\n");
 
 	if(runtime·gotraceback(&crash)) {
-		runtime·traceback((void*)ureg->ip, (void*)ureg->sp, 0, gp);
+		runtime·traceback(ureg->ip, ureg->sp, 0, gp);
 		runtime·tracebackothers(gp);
 		runtime·dumpregs(ureg);
 	}

src/pkg/runtime/os_windows_386.c

@@ -76,7 +76,7 @@ runtime·sighandler(ExceptionRecord *info, Context *r, G *gp)
 	runtime·printf("\n");
 
 	if(runtime·gotraceback(&crash)){
-		runtime·traceback((void*)r->Eip, (void*)r->Esp, 0, gp);
+		runtime·traceback(r->Eip, r->Esp, 0, gp);
 		runtime·tracebackothers(gp);
 		runtime·dumpregs(r);
 	}

src/pkg/runtime/os_windows_amd64.c

@@ -83,7 +83,7 @@ runtime·sighandler(ExceptionRecord *info, Context *r, G *gp)
 	runtime·printf("\n");
 
 	if(runtime·gotraceback(&crash)){
-		runtime·traceback((void*)r->Rip, (void*)r->Rsp, 0, gp);
+		runtime·traceback(r->Rip, r->Rsp, 0, gp);
 		runtime·tracebackothers(gp);
 		runtime·dumpregs(r);
 	}