troff: silence gcc printf warning

src/cmd/troff/n4.c

@@ -559,7 +559,7 @@ void prnumerr(void)
 									warn);
 	if (frame != stk)	/* uncertainty correction */
 		numtabp[CD].val--;
-	ERROR err_buf WARN;
+	ERROR "%s", err_buf WARN;
 	numtabp[CD].val = savcd;
 }
 

src/cmd/troff/n5.c

@@ -467,7 +467,7 @@ void casetm1(int ab, FILE *out)
 			p = chname(c);
 			switch (*p) {
 			case MBchar:
-				sprintf(&tmbuf[i], p+1);
+				strcpy(&tmbuf[i], p+1);
 				break;
 			case Number:
 				sprintf(&tmbuf[i], "\\N'%s'", p+1);