machine/atmega: bufferSize = 32

to save memory on 2k ram targets
also updates sizediff tool to show ram differences

src/machine/buffer.go

@@ -4,8 +4,6 @@ import (
 	"runtime/volatile"
 )
 
-const bufferSize = 128
-
 // RingBuffer is ring buffer implementation inspired by post at
 // https://www.embeddedrelated.com/showthread/comp.arch.embedded/77084-1.php
 type RingBuffer struct {

src/machine/buffer_atmega.go

@@ -0,0 +1,5 @@
+//go:build atmega
+
+package machine
+
+const bufferSize = 32

src/machine/buffer_generic.go

@@ -0,0 +1,5 @@
+//go:build !atmega
+
+package machine
+
+const bufferSize = 128