rename configure.in to configure.ac

Some newer versions of autoconf kvetch if we are still using
configure.in.  As of this writing the only version of autoconf which I
support is autoconf 2.69, and if you try to recreate the configure
script which is shipped with e2fsprogs, and it breaks, you get to keep
both pieces.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
3 files changed