Set install_name to full path on OSX

When building and installing to a non-standard directory on OSX (for
example: when testing multiple versions of CK) it is desirable for
clients of CK to have the install_name match the installed location,
otherwise they need to resort to setting DYLD_LIBRARY_PATH to pick up
the library.
add --with(out)?-pic configure options

This makes configure smell more like standard configure scripts and
easier for larger build systems to control the nature of the build.

When building non-pic, don't build the shared object, as a non-pic
shared object doesn't make a huge amount of sense.