Description:
------------
version_compare seems to return invalid results in two cases:
0.1a vs 0.1 and 1.0.a vs 1.0. in both cases the value on the left should be the newest version.
If the a (alpha) is confusing it, then it does the same for other letters (e.g. M).

Reproduce code:
---------------
$test = array (
	array('0.1', '0.1', 0),
	array('0.1', '0.2', -1),
	array('0.3', '0.2', 1),
	array('0.1.0', '0.1', 1),
	array('0.1a', '0.1', 1),
	array('0.1m', '0.1', 1),
	array('0.1z', '0.1', 1),
	array('0.1a', '0.1b', -1),
	array('0.1.a', '0.1', 1),
	array('0.1.a', '0.1.b', -1),
	array('0.1-pre2', '0.1-pre1', 1),
	array('0.11', '0.2', 1),
	array('0.11.1', '0.2.3', 1)
	);

foreach($test as $vals) {
	$ret = version_compare($vals[0], $vals[1]);
	echo "$vals[0] vs $vals[1] should be $vals[2] and is $ret ...[". ($ret === $vals[2] ? 'PASSED' : 'FAILED') ."]\n";
}


Expected result:
----------------
all of them should return PASSED.

Actual result:
--------------
0.1 vs 0.1 should be 0 and is 0 ...[PASSED]
0.1 vs 0.2 should be -1 and is -1 ...[PASSED]
0.3 vs 0.2 should be 1 and is 1 ...[PASSED]
0.1.0 vs 0.1 should be 1 and is 1 ...[PASSED]
0.1a vs 0.1 should be 1 and is -1 ...[FAILED]
0.1m vs 0.1 should be 1 and is -1 ...[FAILED]
0.1z vs 0.1 should be 1 and is -1 ...[FAILED]
0.1a vs 0.1b should be -1 and is -1 ...[PASSED]
0.1.a vs 0.1 should be 1 and is -1 ...[FAILED]
0.1.a vs 0.1.b should be -1 and is -1 ...[PASSED]
0.1-pre2 vs 0.1-pre1 should be 1 and is 1 ...[PASSED]
0.11 vs 0.2 should be 1 and is 1 ...[PASSED]
0.11.1 vs 0.2.3 should be 1 and is 1 ...[PASSED]