Fix TextField clipping When Scaling Horizontally.

Currently when you scale a TextField horizontally, it will begin to clip the text until nothing is visible.  This PR is an attempt to fix this.

**NOTE:** I really do not have a full grasp of what is going on in TextField.cpp and would appreciate a good review of this before it gets merged.

Please have a look at this sample project that exhibits this issue.  It doesn't occur when applying the changes in this PR.  https://github.com/JandyCo/TextScaleTest

This PR addresses openfl/openfl-native#224.