cmd, core, eth, light, trie: add trie read caching layer

vendor/github.com/allegro/bigcache/bytes.go

@@ -0,0 +1,14 @@
+// +build !appengine
+
+package bigcache
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+func bytesToString(b []byte) string {
+	bytesHeader := (*reflect.SliceHeader)(unsafe.Pointer(&b))
+	strHeader := reflect.StringHeader{Data: bytesHeader.Data, Len: bytesHeader.Len}
+	return *(*string)(unsafe.Pointer(&strHeader))
+}