Don't use '-' in option string to getopt().

@dram reported a build failure in FreeBSD at
https://github.com/davidgiven/ack/issues/1#issuecomment-273668299

Linux manual for getopt(3) says:
> If the first character of optstring is '-', then each nonoption
> argv-element is handled as if it were the argument of an option with
> character code 1....
>
> The use of '+' and '-' in optstring is a GNU extension.

GNU/Linux and OpenBSD handle '-' in this special way, but FreeBSD
seems not to.  If '-' is not special, then em_ego can't find its input
file, so the build must fail.  This commit stops using '-' in both
em_b and em_ego, but doesn't change mcg.

Also fix em_ego -O3 to not act like -O4.

lang/b/compiler/b0.c

@@ -34,12 +34,19 @@ init(char *s, int val)
 	np->offset = val;
 }
 
+static void
+usage(void)
+{
+	error("Usage: em_b [-w wordsize] [-B modulename] [-i inputfile] [-o outputfile]");
+	exit(1);
+}
+
 int
 main(int argc, char *argv[])
 {
 
 	for (;;) {
-		int opt = getopt(argc, argv, "-w:B:i:o:");
+		int opt = getopt(argc, argv, "w:B:i:o:");
 		if (opt == -1)
 			break;
 
@@ -66,11 +73,12 @@ main(int argc, char *argv[])
 				}
 				break;
 
-			derfault:
-				error("Usage: em_b [-w wordsize] [-B modulename] [-i inputfile] [-o outputfile]");
-				exit(1);
+			default:
+				usage();
 		}
 	}
+	if (optind < argc)
+		usage();
 
 	init("auto", AUTO);
 	init("extrn", EXTERN);

util/ego/em_ego/em_ego.c

@@ -346,7 +346,7 @@ int main(int argc, char* argv[])
 	opterr = 0;
 	for (;;)
 	{
-		int opt = getopt(argc, argv, "-M:P:O:vt");
+		int opt = getopt(argc, argv, "M:P:O:vt");
 		if (opt == -1)
 			break;
 
@@ -364,17 +364,14 @@ int main(int argc, char* argv[])
 			{
 				int o = atoi(optarg);
 				if (o <= 2)
-					break;
-				if (o <= 3)
+					Ophase = &O2phases[0];
+				else if (o == 3)
 					Ophase = &O3phases[0];
-				Ophase = &O4phases[0];
+				else
+					Ophase = &O4phases[0];
 				break;
 			}
 
-			case 1:
-				add_file(optarg);
-				break;
-
 			case 't':
 				keeptemps = 1;
 				goto addopt;
@@ -390,6 +387,9 @@ int main(int argc, char* argv[])
 		}
 	}
 
+	for (i = optind; i < argc; i++)
+		add_file(argv[i]);
+
 	phase_args[nphase_args] = 0;
 	if (nuphases)
 		Ophase = uphases;