autoconf: Use libtool, not dolt replacement.

Dolt doesn't provide the performance benefits it promises, so drop it
to simplify the moving parts of the Autotools build system.

Also remove unused M4 modules.

* m4/dolt.m4: Delete file.
* m4/ax_boost_base.m4: Likewise.
* configure.ac: Do not call DOLT.

Change-Id: I58d286457005ad82129e089679c52933989c59a8