libbb: introduce and use common crc32 routine

function                                             old     new   delta
crc32_block_endian1                                    -      37     +37
crc32_block_endian0                                    -      34     +34
global_crc32_table                                     -       8      +8
file_read                                             82      87      +5
gzip_main                                            211     214      +3
xz_crc32                                              40      35      -5
crc32_table                                            8       -      -8
calculate_gunzip_crc                                  54      34     -20
lzo_crc32                                             54      25     -29
cksum_main                                           298     211     -87
------------------------------------------------------------------------------
(add/remove: 3/1 grow/shrink: 2/4 up/down: 87/-149)           Total: -62 bytes

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
diff --git a/coreutils/cksum.c b/coreutils/cksum.c
index 7bf383e..7a37e6a 100644
--- a/coreutils/cksum.c
+++ b/coreutils/cksum.c
@@ -18,7 +18,6 @@
 	off_t length, filesize;
 	int bytes_read;
 	int exit_code = EXIT_SUCCESS;
-	uint8_t *cp;
 
 #if ENABLE_DESKTOP
 	getopt32(argv, ""); /* coreutils 6.9 compat */
@@ -39,11 +38,7 @@
 
 #define read_buf bb_common_bufsiz1
 		while ((bytes_read = safe_read(fd, read_buf, sizeof(read_buf))) > 0) {
-			cp = (uint8_t *) read_buf;
-			length += bytes_read;
-			do {
-				crc = (crc << 8) ^ crc32_table[(crc >> 24) ^ *cp++];
-			} while (--bytes_read);
+			crc = crc32_block_endian1(crc, read_buf, bytes_read, crc32_table);
 		}
 		close(fd);