tforms that have shared libs.
* New '-allow-undefined' link flag to build shared libs that contain
  references to unresolved symbols.
* Removed all support for creating static-only libraries.
* Basic support for dynamically loaded modules: new '-export-dynamic'
  linking flag and corresponding 'dlname' mode.
* New '--features' flag to display configured libtool attributes.
* Added support for installing libtool objects, both in absolute and
  relative directories.
* Support *-*-linux-gnu* as an alias for *-*-linux*.
* Support for *-*-openbsd* and *-*-freebsd3*.