#39 wxKeyBinder does not support non-alphanumeric key codes as shortcuts

[Roberto Perpuly]

When wxKeyBinder converts a shortcut string to key codes, it is missing mappings of non-ascii keycodes > 300; users cannot create bindings with keys such as Left arrow, page up, and such.

Steps to reproduce:
1. run the keybinder minimal program
2. go to File .. keybindings
3. select the "File|shortcuts" category
4. for the command shortcut 1, add the shortcut "CTRL+SHIFT+DOWN" (down arrow)

notice that the shortcut is incorrectly added as CTRL+SHIFT+D

Patch that fixes the issue has been attached to this ticket.