refactor(charset)!: delete 'isprint' and cleanup 'iskeyword' and friends

In the `enc=utf-8` only world, the 'isprint' option is quite obsolete.
The function is only consulted for decoded U+0080 to U+00FF chars
whose printability is defined by the unicode charset, just like
higher codepoints. Meanwhile, invalid `\x80` to `\xFF` bytes are always
unprintable.

Disentangle 'iskeyword', 'isfname' and 'isident' from each other by
giving them all separate bitsets. Now these can be updated individually.
These updaters can back out of errors gracefully, no need for extra
panic logic in option[str].c to restore partially updated chartabs.

1 files changed, 0 insertions, 6 deletions

diff --git a/test/functional/vimscript/json_functions_spec.lua b/test/functional/vimscript/json_functions_spec.lua
index ed9a84083e..be37aa8e0d 100644
--- a/test/functional/vimscript/json_functions_spec.lua
+++ b/test/functional/vimscript/json_functions_spec.lua
@@ -972,12 +972,6 @@ describe('json_encode() function', function()
     )
   end)
 
-  it('ignores improper values in &isprint', function()
-    api.nvim_set_option_value('isprint', '1', {})
-    eq(1, eval('"\1" =~# "\\\\p"'))
-    eq('"\\u0001"', fn.json_encode('\1'))
-  end)
-
   it('fails when using surrogate character in a UTF-8 string', function()
     eq(
       'Vim(call):E474: UTF-8 string contains code point which belongs to a surrogate pair: \237\160\128',