The use_legacy_coding function is an extension to the curses
library. It allows the caller to change the result of unctrl,
and suppress related checks within the library that would
normally cause nonprinting characters to be rendered in visible
form. This affects only 8-bit characters.
The level parameter controls the result:
0 the library functions normally, rendering nonprinting
characters as described in unctrl.
1 the library ignores isprintf for codes in the range
2 the library ignores isprintf for codes in the range
128-255. It also modifies the output of unctrl,
showing codes in the range 128-159 as is.
This routine is specific to ncurses. It was not supported on
Version 7, BSD or System V implementations. It is recommended
that any code depending on ncurses extensions be conditioned
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