tidy-up: miscellaneous

- avoid "will" in builds scripts, scripts folder, curl_easy_ssls_export.md,
  and few other files.
- badwords: add "initialise", "nul terminated", "thread safety" and
  variations.
- prefer "null-terminat", where missing (two places).
- fix "null-terminat*" missing dash.
- hostip: merge two `#if` blocks.
- tool_doswin: fix comment
  Spotted by GitHub Code Quality
  Follow-up to 9a2663322c #17572
- fix stray spaces and newlines.

Closes #21638

src/var.c

@@ -355,7 +355,7 @@ static ParameterError addvariable(const char *name,
   p = curlx_calloc(1, sizeof(struct tool_var) + nlen);
   if(p) {
     memcpy(p->name, name, nlen);
-    /* the null termination byte is already present from above */
+    /* the null-termination byte is already present from above */
 
     p->content = contalloc ? content : curlx_memdup0(content, clen);
     if(p->content) {