Extend autotools build to create shared library libopenocd with libtool:

Extend autotools build to create shared library libopenocd with libtool:
- Add libtoolize step too bootstrap script; creates ltmain.sh script.
- Add AC_PROG_LIBTOOL to configure.in to add libtool support to build.
- Change Makefile.am library rules from static (_a) to libtool (_la).
- Install libopenocd.{la,so,a} in $(libdir); update openocd link rules.
- Extend MAINTAINERCLEANFILES in top-level Makefile.am to remove ltmain.sh.

git-svn-id: svn://svn.berlios.de/openocd/trunk@1695 b42882b7-edfa-0310-969c-e2dbd0fdcd60