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/getpart.pm

@@ -54,7 +54,7 @@ my $trace=0;
 
 # Normalize the part function arguments for proper caching. This includes the
 # filename in the arguments since that is an implied parameter that affects the
-# return value.  Any error messages will only be displayed the first time, but
+# return value.  Any error messages are only displayed the first time, but
 # those are disabled by default anyway, so should never been seen outside
 # development.
 sub normalize_part {
@@ -195,7 +195,7 @@ sub partexists {
 }
 
 # The code currently never calls this more than once per part per file, so
-# caching a result that will never be used again just slows things down.
+# caching a result that is never used again just slows things down.
 # memoize('partexists', NORMALIZER => 'normalize_part');  # cache each result
 
 sub loadtest {