On sun, use stlport.

Fixes #2772.


[SVN r51894]

Jamroot

@@ -196,6 +196,9 @@ project boost
       # Used to encode variant in target name. See the 'tag' rule below.
       <tag>@$(__name__).tag
       <conditional>@handle-static-runtime
+      # The standard library Sun compilers use by default has no chance
+      # of working with Boost. Override it.
+      <toolset>sun:<stdlib>sun-stlport
     : usage-requirements <include>.
     : build-dir bin.v2
     : default-build $(default-build)