Add ASCII control codes

[bbx10]

0x00 CTRL-@ through 0x1F CTRL-_

Also return ASCII codes for keys: ESCAPE, DELETE, and TAB.
Return correct code for ENTER key.

[per1234]

As you say in #5:

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

But you forgot to close this PR @bbx10.

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