Fixed bug where certain characters weren't showing up in text input fields on ios + android.

Bug is due to mobile devices reporting only the ASCII character codes and not the keyboard scan codes like desktop + flash. Treating the ASCII codes as scan codes causes conflicts (eg. periods being treated as DELETE).

Added a translation function to convert ASCII codes on mobile to their keyboard scan code equivalents.

Note this change was developed and tested against openfl-native version 1.1.4. I wasn't able to test it against the latest Git repos as my projects kept crashing (on file reading and HTTP operations - complaining about missing class org/haxe/nme/GameActivity even though i couldn't find any references to it in my code or in lime code).