Improve multi-line kernel ident parsing

Instead of blindly grabbing the line with 'Version string' and the
following one from the core info file, take all lines after 'Version
string' until the one one that matches the field format in the core info
file.  This provides compatibility with VendorBSD modifications that have
a different kernel ident format.

Reviewed by:	jhb

usr.sbin/crashinfo/crashinfo.sh

@@ -45,10 +45,11 @@ find_kernel()
 		nextline=1
 		next
 	}
-	// {
-		if (nextline) {
-			print
+	nextline==1 {
+		if ($0 ~ "^  [A-Za-z ]+: ") {
 			nextline=0
+		} else {
+			print
 		}
 	}' $INFO)