getty: code cleanup, part 1

[des]

Summary

• Avoid unnecessary use of unsigned char *
• Use explicit casts when assigning unsigned char * to char * or vice versa
• Drop unused global variables (and fix memory leak in gettable())
• Use snprintf() instead of strcpy() + strcat()
• Drop spurious braces in switch

Sponsored by: Klara, Inc.
Obtained from: Apple OSS Distributions (in part)

[allanjude]

Reviewed by: allanjude

[pstef]

If you intend to do more work on these files, I suggest improving the style before introducing more significant changes. There is a lot of inherited stylistic issues here, unfortunately.
I think you have a typo in the description and you meant "braces" - I meantion it just in case you planned to copy it to the commit message.

libexec/getty/chat.c

276

missed opportunity to improve formatting

[des]

Update commit message