allocateHash: fix incorrect sizeof computation (#149)

This was supposed to be fixed by 3.12.3-21-g8523cb3 but it was not
because there was a typo sizeof(sizeof ...) and even after fixing
the typo it referred to the pointer size, instead of struct size.

Luckily, this was detected by Clang analyzer again.  Now I verified
that the defect goes away with this commit:

FIXED DEFECTS
=============
Error: CLANG_WARNING:
logrotate.c:249:15: warning: Result of 'malloc' is converted to a pointer of type 'struct logStateList', which is incompatible with sizeof operand type 'unsigned long'

logrotate.c

@@ -246,7 +246,7 @@ static int allocateHash(unsigned int hs)
 	}
 	for (i = 0; i < hs; i++) {
-		states[i] = malloc(sizeof(sizeof states[i]));
+		states[i] = malloc(sizeof *states[0]);
 		if (states[i] == NULL) {
 			message(MESS_ERROR, "could not allocate memory for "
 				"hash element\n");