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

scripts/checksrc.pl

@@ -1199,7 +1199,7 @@ sub scanfile {
         # A rather more interesting, and correct, check would be to not test
         # only locally committed files but inspect all files wrt the year of
         # their last commit. Removing the `git rev-list origin/master..HEAD`
-        # condition below will enforce copyright year checks against the year
+        # condition below enforces copyright year checks against the year
         # the file was last committed (and thus edited to some degree).
         my $commityear = undef;
         @copyright = sort {$$b{year} cmp $$a{year}} @copyright;