core.lua: Fix KEYSTR_RESET sequence

[jlduran_gmail.com]

Summary

Use \027[H\027[J to reset the terminal in Lua (for now), as \027c produces bogus characters and does not clear the terminal.

Test Plan

echo "end" > /boot/lua/local.lua
shutdown -r now
...
Type '?' for a list of commands, 'help' for more detailed help.
OK printc("\027c")
?cOK

Evidently, that is not what we want. As a workaround:

OK printc("\027[H\027[J")

Almost works (does not reset the colors), but is better than what we currently have.

OK boot

[imp]

A lot depends on which terminal emulator you are on.

KEYSTR_RESET is defined to be ESCAPE c in the standards. Most terminal emulators get this right. It also resets attributes and other things that the clear screen sequence that you propose does not.

Given the diversity of terminal emulators in the wild, I'd be quite hesitant to make this change...

[jlduran_gmail.com]

In D34532#782394, @imp wrote:

A lot depends on which terminal emulator you are on.

You are right, I should have specified this originally.

Given the diversity of terminal emulators in the wild, I'd be quite hesitant to make this change...

Can we have _both_ clearing methods? I can propose a different revision then.

Thanks!