Python CPP implementation now requires c++ libprotobuf installed before running

setup.py to fix RPATH problem.

python/README.txt

@@ -63,9 +63,9 @@ Installation
      $ python setup.py install
 
    This step may require superuser privileges.
-   NOTE: To use C++ implementation, you need to export the environment variable
-   before this step. See the "C++ Implementation" section below for more
-   details.
+   NOTE: To use C++ implementation, you need to install C++ protobuf runtime
+   library of the same version and export the environment variable before this
+   step. See the "C++ Implementation" section below for more details.
 
 Usage
 =====
@@ -83,7 +83,10 @@ WARNING: This is EXPERIMENTAL and only available for CPython platforms.
 The C++ implementation for Python messages is built as a Python extension to
 improve the overall protobuf Python performance.
 
-To use the C++ implementation, export an environment variable:
+To use the C++ implementation, you need to:
+1) Install the C++ protobuf runtime library, please see instructions in the
+   parent directory.
+2) Export an environment variable:
 
   $ export PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=cpp
 

python/setup.py

@@ -114,10 +114,8 @@ if __name__ == '__main__':
         [ "google/protobuf/pyext/python_descriptor.cc",
           "google/protobuf/pyext/python_protobuf.cc",
           "google/protobuf/pyext/python-proto2.cc" ],
-        include_dirs = [ "../src", ".", ],
-        libraries = [ "protobuf" ],
-        runtime_library_dirs = [ "../src/.libs" ],
-        library_dirs = [ "../src/.libs" ]))
+        include_dirs = [ "." ],
+        libraries = [ "protobuf" ]))
 
   setup(name = 'protobuf',
         version = '2.4.1-pre',