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

tests/devtest.pl

@@ -94,7 +94,7 @@ sub parseprotocols {
     # Generate a "proto-ipv6" version of each protocol to match the
     # IPv6 <server> name and a "proto-unix" to match the variant which
     # uses Unix domain sockets. This works even if support is not
-    # compiled in because the <features> test will fail.
+    # compiled in because the <features> test fails.
     push @protocols, map(("$_-ipv6", "$_-unix"), @protocols);
 
     # 'http-proxy' is used in test cases to do CONNECT through