build: make `CURL_FORMAT_CURL_OFF_T[U]` work with mingw-w64 <=7.0.0

build: make `CURL_FORMAT_CURL_OFF_T[U]` work with mingw-w64 <=7.0.0

Add tweak for mingw-w64 when building tests/http/client programs to
avoid a bogus `-Wformat` warning when using mingw-w64 v7.0.0 or older.
The warning is bogus because these programs use curl's `printf()`
implementation that is guaranteed to support that format spec.

Add this for both CMake and autotools. (But only CMake is CI tested with
an old toolchain.)

Apply the workaround to `docs/examples`, and fix an example to use
curl's `printf()` with `CURL_FORMAT_CURL_OFF_T`.

Reintroduce curl `printf()` calls into `tests/http/client`, via #14625.
Also restore large number masks to a printf, changed earlier in #14382.

Follow-up to 232302f88a152a1d1722da9f69c383a766528918 #14382
Ref: https://github.com/curl/curl/pull/14625#issuecomment-2302361737

Closes #14640