fix max-pkts option inconsistencies

This is for RH bug 498426,
btrecord doesn't recognize --max-pkts and --max-packets cmd line options

Usage text and some documentation references "--max-pkts" and the man page references "--max-packets" but the getopts code is looking for --max_pkts.

I'm not sure if it's best to make the code match the majority of the docs, or fix the docs to match the code? This patch does the former, but I'm not picky if you want to go the other way :)

---

index 09329f7..88ab806 100644
@@ -152,7 +152,7 @@ static struct option l_opts[] = {
 		.val = 'm'
 	},
 	{
-		.name = "max_pkts",
+		.name = "max-pkts",
 		.has_arg = required_argument,
 		.flag = NULL,
 		.val = 'M'

index f8477da..b4318ae 100644
@@ -121,7 +121,7 @@ The default value is 10,000,000 nanoseconds (10 milliseconds).
 
 \-M <\fInum\fR>
 .br
-\-\-max\-packets=<\fInum\fR>
+\-\-max\-pkts=<\fInum\fR>
 .RS
 Set maximum number of packets per bunch.
 The \fI\-M\fR option requires a single parameter which specifies the