Sign text line length is limited differently on Win10 than PE

In Windows 10 Edition, I can type characters up to the width of the sign. In PE, the length is limited to 15 characters no matter what I type.

This affects both singleplayer and multiplayer

Devices and versions:

• Lenovo G50-80 - Win10 Edition 1.0.2
• LG G5 - Pocket Edition 1.0.2