Thrift: Python installation.

Summary:
Added the configure script variable PY_PREFIX which serves the same purpose
for Python as --prefix does for C/C++.  We chose to do this because Python
has different conventions for where to install libraries.

Reviewed By: mcslee

Test Plan:
Full clean builds and installs of Thrift from the Thrift root,
with and without PY_PREFIX.  Watched output of make install.

Ran configure from lib/py without PY_PREFIX, with PY_PREFIX and with
PY_PREFIX in the environment.  Checked config.status for each.

Revert Plan: okay


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665248 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/py/README b/lib/py/README
index bdd2ef1..3a5ba92 100644
--- a/lib/py/README
+++ b/lib/py/README
@@ -1,7 +1,7 @@
 Thrift Python Software Library
 
 Author: Mark Slee (mcslee@facebook.com)
-Last Modified: 2007-Mar-05
+Last Modified: 2007-Sep-04
 
 Thrift is distributed under the Thrift open source software license.
 Please see the included LICENSE file.
@@ -13,7 +13,8 @@
 thrift, and there are subpackages for the protocol, transport, and server
 code. Each package contains modules using standard Thrift naming conventions
 (i.e. TProtocol, TTransport) and implementations in corresponding modules
-(i.e. TSocket).
+(i.e. TSocket).  There is also a subpackage reflection, which contains
+the generated code for the reflection structures.
 
 The Python libraries can be installed manually using the provided setup.py
 file, or automatically using the install hook provided via autoconf/automake.