Fix #782 - websocketservice.js garbles input on Banana Pi running Armbian

Fix #782 (closed) - A sysop running Armbian on a Banana Pi reported garbled input when connecting via fTelnet and websocketservice.js. This is because the bytes aren't being unmasked correctly, which is likely due to a buggy javascript library that isn't handling the for loop correctly. Refactoring how the bytes are unmasked works around whatever the issue is (for now?)

assigned to @rswindell

merged

mentioned in commit 72f27c93