fix(inputs): ignoring input events in IE caused by placeholder changes o...

...r focus/blur on inputs with placeholders

This is my attempt at fixing #8242 as well as the extra placeholder issues with focus/blur. I'm assuming I'm missing a weird test case that still breaks somewhere, but I still think this is an improvement (it definitely is for my use cases).
This is the case in which https://github.com/jbedard/angular.js/commit/e65327548dbb0dea65677b302989bd5b30cc29a2 would still fail. A placeholder change while the input is in focus (with or without a value) does NOT emit the extra input event, but we would still set the flag to ignoreNextInput.