leading zeros after hashing are not dropped on M1 and M2

[simon]

The PHP code is tested against the JS code. The JS code is tested against the Java code in the other repos. The Java BigInteger logic strips leading zeros when it converts to hex. This means that the JS code has to strip leading zeros to be compatible with the Java code. This means that the PHP code has to strip leading zeros also.

[simon]

resolved and added a unit test which checks 100 verifications using values output from the Java code.