#2 Solaris R path variable in configure script

[Rainer Machne]

Within a previous bug report Tommi Aho had reported for
SOSlib 1.6.0pre:

In Solaris 2.9, I additionally changed
SBML_RPATH="-Wl,-rpath,$with_libsbml/lib"
to
SBML_RPATH="-Wl,-R$with_libsbml/lib"
because the dynamic linker was confused by the switch
-rpath.