Fix for assignment from string not resetting sign bit, see: https://svn.boost.org/trac/boost/ticket/9936
New jamfile to run all examples (showing compile fail in cpp_bin_float).

Some only work if gmp, mpir, mpfr, tommath are installed, of course.
Fix compilation of examples, plus Jamfile, plus one comparison bug in cpp_bin_float.
Merge branch 'develop'