function_base.hpp, function_template.hpp:

  - Use a vtable instead of separate manager/invoker pointers, to shrink the
    size of a boost::function object to 8 bytes
  - Fix a problem with NULL member pointers


[SVN r32186]

libs/function

@@ -1 +1 @@
-Subproject commit c5e64fab9930ccc9f252e0908b37055782539207
+Subproject commit 93c691fbdf9b2d786adcedf3fb577eb2faa1a3e4