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