Merge branch 'bc/drop-ancient-libcurl-and-perl'

Drop support for older libcURL and Perl. * bc/drop-ancient-libcurl-and-perl: gitweb: make use of s///r Require Perl 5.26.0 INSTALL: document requirement for libcurl 7.61.0 git-curl-compat: remove check for curl 7.56.0 git-curl-compat: remove check for curl 7.53.0 git-curl-compat: remove check for curl 7.52.0 git-curl-compat: remove check for curl 7.44.0 git-curl-compat: remove check for curl 7.43.0 git-curl-compat: remove check for curl 7.39.0 git-curl-compat: remove check for curl 7.34.0 git-curl-compat: remove check for curl 7.25.0 git-curl-compat: remove check for curl 7.21.5