Add ASCII control codes

[bbx10]

KeyboardReportParser::OemToAscii does not return ASCII control codes such as CTRL-A (0x01). It also does not return ASCII codes for the following keys: TAB, ESCAPE, and DELETE. It returns the wrong code for the ENTER key.

The proposed patch to has been submitted: #4

[bbx10]

Closed PR #4 to add fixes from @dewhisna. The latest patch is PR #7.