Merge branch 'backport/jk/libcurl-8.7-regression-workaround' into maint-2.39

Fix was added to work around a regression in libcURL 8.7.0 (which has already been fixed in their tip of the tree). * jk/libcurl-8.7-regression-workaround: remote-curl: add Transfer-Encoding header only for older curl INSTALL: bump libcurl version to 7.21.3 http: reset POSTFIELDSIZE when clearing curl handle Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>