Replace int -> uint to avoid signed integer overflow

An example of such an error (should be compiled with DEBUG_SANITIZE):

runtime error: left shift of 1 by 31 places cannot be represented in
type 'int'

Signed-off-by: Rostislav Skudnov <rostislav@tuxera.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

libbb/crc32.c

@@ -24,7 +24,7 @@ uint32_t* FAST_FUNC crc32_filltable(uint32_t *crc_table, int endian)
 {
 	uint32_t polynomial = endian ? 0x04c11db7 : 0xedb88320;
 	uint32_t c;
-	int i, j;
+	unsigned i, j;
 
 	if (!crc_table)
 		crc_table = xmalloc(256 * sizeof(uint32_t));