using == where possible instead of ~ in mkdevc's awk implementation
avoids having device drivers that happen to contain "ad" and "sd"
anywhere in their names trigger the special handling for devad and devsd.
also use equality to detect section names.
in two cases ~ remains where it is conveniently doing a pattern match
against section names and objtypes, where no confusion should arise.

Reference: /n/sources/patch/applied/mkdevc-equality
Date: Wed Jul  8 16:45:50 CES 2009
Signed-off-by: forsyth@terzarima.net

--- /sys/src/9/port/mkdevc	Wed Jul  8 16:45:13 2009
+++ /sys/src/9/port/mkdevc	Wed Jul  8 16:45:10 2009
@@ -15,28 +15,28 @@
 collect && /^[^ \t]/{
 	collect = 0;
 }
-collect && section ~ "dev"{
+collect && section == "dev"{
 	dev[ndev++] = $1;
-	if($1 ~ "ad")
+	if($1 == "ad")
 		devad = 1;
-	else if($1 ~ "sd")
+	else if($1 == "sd")
 		devsd = 1;
-	else if($1 ~ "uart")
+	else if($1 == "uart")
 		devuart = 1;
-	else if($1 ~ "vga")
+	else if($1 == "vga")
 		devvga = 1;
 	for(i = 2; i <= NF; i++){
-		if($i ~ "dma" && objtype ~ "(386|alpha|amd64)")
+		if($i == "dma" && objtype ~ "(386|alpha|amd64)")
 			i8237dma++;
 	}
 }
-collect && section ~ "ip"{
+collect && section == "ip"{
 	ip[nip++] = $1;
 }
-collect && section ~ "link"{
+collect && section == "link"{
 	link[nlink++] = $1;
 }
-collect && section ~ "misc"{
+collect && section == "misc"{
 	sub(/^[ \t]*/, "");
 	misc[nmisc++] = $1;
 	if($1 ~ "^arch.*")
@@ -59,13 +59,13 @@
 	}
 }
 
-collect && section ~ "port"{
+collect && section == "port"{
 	sub(/^[ \t]*/, "");
 	port[nport++] = $0;
 }
 $0 ~ /^[^ \t]/{
-	if($0 ~ "(bootdir|dev|ip|link|misc|port)"){
-		section = $0;
+	if($1 ~ "(bootdir|dev|ip|link|misc|port)"){
+		section = $1;
 		collect = 1;
 	}
 	next;
@@ -109,7 +109,7 @@
 		printf "\t%slink();\n", link[i];
 	printf "}\n\n";
 
-	if(narch || objtype ~ "386"){
+	if(narch || objtype == "386"){
 		for(i = 0; i < narch; i++)
 			printf "extern PCArch %s;\n", arch[i];
 		printf "PCArch* knownarch[] = {\n";