Implemented walker overlay that calculates decompressed size.

espReader/ESPReader.h

@@ -267,6 +267,11 @@ extern "C" {
 	 */
 	void espr_print(char *data, size_t size);
 
+	/* Calculates the size of the esp data if all of the compressed records are
+	 * decompressed.
+	 */
+	size_t espr_decompressed_size(char *data, size_t size);
+
 // End C++ guard
 #ifdef __cplusplus
 }