autoconf --warnings=all resulted in
warning: The macroAC_HELP_STRING' is obsolete.`
warning: The macro
libcurl.m4: Avoid obsolete warning
By analyzing the blame information on this pull request, we identified @bagder, @yangtse and @dwlocks to be potential reviewers
This seems fine. AS_HELP_STRING was apparently introduced in autoconf 2.58, released in November 2003.