refactor: remove char_u (#22829)

Closes https://github.com/neovim/neovim/issues/459

src/nvim/generators/gen_ex_cmds.lua

@@ -41,7 +41,7 @@ static const uint16_t cmdidxs1[%u] = {
 -- Values in cmdidxs2[c1][c2] are relative to cmdidxs1[c1] so that they
 -- fit in a byte.
 local cmdidxs2_out = string.format([[
-static const char_u cmdidxs2[%u][%u] = {
+static const uint8_t cmdidxs2[%u][%u] = {
   /*           a   b   c   d   e   f   g   h   i   j   k   l   m   n   o   p   q   r   s   t   u   v   w   x   y   z */
 ]], a_to_z, a_to_z)
 

src/nvim/generators/gen_options.lua

@@ -139,7 +139,7 @@ local dump_option = function(i, o)
     w(get_cond(o.enable_if))
   end
   if o.varname then
-    w('    .var=(char_u *)&' .. o.varname)
+    w('    .var=(char *)&' .. o.varname)
   elseif #o.scope == 1 and o.scope[1] == 'window' then
     w('    .var=VAR_WIN')
   end