Query stopwords: Only eliminate single A-Z letters as search terms.

Merges [25954] to the 3.7 branch.

Stop trying to match any single letters that are not East Asian characters, as this requires PCRE with UTF-8 support; and because it doesn't actually work.

fixes #25709.

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When an HTTPS request to api.wordpress.org fails, try an insecure HTTP request and issue a warning.

Certain versions of cURL appear to claim OpenSSL support but fail to work. We need to not trap users on older versions while we work this out, and instead fall back to an insecure request.

Merges [25956] to the 3.7 branch.
fixes #25716 for the 3.7 branch.

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3.7-RC1

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