You should first read the introductory portions of the automake
Manual, if you are not already familiar with it.
-Two files are needed, 'configure.in', which is used to build the
+Two files are needed, 'configure.ac', which is used to build the
configure script:
-==configure.in===
+==configure.ac===
dnl Process this file with autoconf to produce a configure script.
AC_INIT(testinput.c)