deps: update images to v0.18.0

Update the images dependency to v0.18.0
This includes a change in the Fedora IoT remote configuration which is
now installed through an RPM instead of being hard-coded in the image
definitions.

vendor/github.com/klauspost/compress/fse/bitwriter.go

@@ -152,12 +152,11 @@ func (b *bitWriter) flushAlign() {
 
 // close will write the alignment bit and write the final byte(s)
 // to the output.
-func (b *bitWriter) close() error {
+func (b *bitWriter) close() {
 	// End mark
 	b.addBits16Clean(1, 1)
 	// flush until next byte.
 	b.flushAlign()
-	return nil
 }
 
 // reset and continue writing by appending to out.

vendor/github.com/klauspost/compress/fse/compress.go

@@ -199,7 +199,8 @@ func (s *Scratch) compress(src []byte) error {
 	c2.flush(s.actualTableLog)
 	c1.flush(s.actualTableLog)
 
-	return s.bw.close()
+	s.bw.close()
+	return nil
 }
 
 // writeCount will write the normalized histogram count to header.
@@ -211,7 +212,7 @@ func (s *Scratch) writeCount() error {
 		previous0 bool
 		charnum   uint16
 
-		maxHeaderSize = ((int(s.symbolLen) * int(tableLog)) >> 3) + 3
+		maxHeaderSize = ((int(s.symbolLen)*int(tableLog) + 4 + 2) >> 3) + 3
 
 		// Write Table Size
 		bitStream = uint32(tableLog - minTablelog)