Description:
------------
Now adler32 algorithm for each byte uses two operations " % 65521". It is very slow.
I propose to change the function PHP_ADLER32Update in the file hash_adler32.c
{
	php_hash_uint32 i, s[2];
	
	s[0] = context->state & 0xffff;
	s[1] = (context->state >> 16) & 0xffff;
	for (i = 0; i < len; ++i) {
		s[0] += input[i];
		s[1] += s[0];
		if (s[1]>0x7fffffff)
		{
			s[0] = s[0] % 65521;
			s[1] = s[1] % 65521;
		}
	}
	s[0] = s[0] % 65521;
	s[1] = s[1] % 65521;
	context->state = s[0] + (s[1] << 16);
}

Test script:
---------------
<?php
$t = microtime(true);
echo hash_file('adler32','/home/user/testfile')."\n"; // I used testfile size 400 MB with random content
echo sprintf('%0.3d',(microtime(true)-$t)*1000)." ms\n\n";
?>

Actual result:
--------------
PHP 5.3.3 showed:
85ffb2c5
2174 ms

After modification the file:
85ffb2c5
664 ms

Speed was higher than about 3 times