add LSB-first comment and Poly value

crc/crc32.c

@@ -3,6 +3,12 @@
 **
 ** Author:Wang Yaofu voipman@qq.com
 ** Description: The source file of class crc32.
+**  CRC32 implementation according to IEEE standards.
+**  Polynomials are represented in LSB-first form
+**  following parameters:
+**    Width                      : 32 bit
+**    Poly                       : 0xedb88320 (That is actually x^8 + x^5 + x^4 + 1)
+**    Output for "123456789"     : 0xCBF43926
 */
 #include <stdlib.h>
 #include "crc32.h"