Log Message:
Update to 0.9.  Changes in this version:

     o   Distribution documents converted to mdoc.

     o   Improved the bt_generate_output() function in bt_config; it now gen-
         erates an external script, called bt_output, that can be used to
         recreate files at any time.

     o   Implemented Buildtool version checking (BT_REQUIRE can be used now).
         We cannot wait until 1.0 to have this feature.

     o   Miscellaneous bug fixes (in bt_config and bt_lint).

     o   Automatically generated configuration files have been prefixed with
         `bt_' to avoid conflicts with user files.  For example, config.h is
         now named bt_config.h by default.

     o   Support for shared libraries has now been disabled by default.  It is
         still too incomplete.