http: give curl version warnings consistently

http: give curl version warnings consistently

When a requested feature cannot be activated because the version of
cURL library used to build Git with is too old, most of the codepaths
give a warning like "$Feature is not supported with cURL < $Version",
marked for l10n.  A few of them, however, did not follow that pattern
and said things like "$Feature is not activated, your curl version is
too old (>= $Version)", and without marking them for l10n.

Update these to match the style of the majority of warnings and mark
them for l10n.

Signed-off-by: Junio C Hamano <gitster@pobox.com>