GitLab

AC_HELP_STRING -> AS_HELP_STRING
AC_TRY_COMPILE -> AC_COMPILE_IFELSE([AC_LANG_PROGRAM([...])],...)
AC_CONFIG_HEADER -> AC_CONFIG_HEADERS
AC_PROG_LIBTOOL -> LT_INIT

Note: There might be more deprecated macros that I haven't noticed.
I just wish to avoid painful highlighting from my text editor (gedit)
that complains about them. :)