I started using m4_esyscmd_s to implement CDRIVER-1013. It's a macro that runs a system command and trims whitespace from the output:

m4_esyscmd_s(cat VERSION_CURRENT)

That works with my version of autoconf, 2.69, but it's not available in autoconf 2.63 on RHEL 6.2. Instead, do:

        m4_esyscmd(cat VERSION_CURRENT | tr -d '\n')