VERSION, params: start Geth 1.5.6 development cycle

VERSION

@@ -1 +1 @@
-1.5.5
+1.5.6

params/version.go

@@ -19,10 +19,10 @@ package params
 import "fmt"
 
 const (
-	VersionMajor = 1        // Major version component of the current release
-	VersionMinor = 5        // Minor version component of the current release
-	VersionPatch = 5        // Patch version component of the current release
-	VersionMeta  = "stable" // Version metadata to append to the version string
+	VersionMajor = 1          // Major version component of the current release
+	VersionMinor = 5          // Minor version component of the current release
+	VersionPatch = 6          // Patch version component of the current release
+	VersionMeta  = "unstable" // Version metadata to append to the version string
 )
 
 // Version holds the textual version string.