[#1543] Fix missing C++11 flag for building python bindings

* Extract the flags from CXX and put into CXXFLAGS which is
   passed into setup.py extra_compile_args.
 * Remove now redundant os.environ test in setup.py

bindings/python/compile_flags.in

@@ -1 +1 @@
--I@top_srcdir@/include @COMPILETIME_OPTIONS@ @CPPFLAGS@ @BOOST_CPPFLAGS@ @OPENSSL_INCLUDES@
+-I@top_srcdir@/include @COMPILETIME_OPTIONS@ @CXXFLAGS@ @CPPFLAGS@ @BOOST_CPPFLAGS@ @OPENSSL_INCLUDES@

bindings/python/setup.py

@@ -112,13 +112,6 @@ else:
 		extra_link = flags.parse(ldflags)
 		extra_compile = flags.parse(extra_cmd)
 
-		# for some reason distutils uses the CC environment variable to determine
-		# the compiler to use for C++
-		if 'CXX' in os.environ:
-			os.environ['CC'] = os.environ['CXX']
-		if 'CXXFLAGS' in os.environ:
-			os.environ['CFLAGS'] = os.environ['CXXFLAGS']
-
 		ext = [Extension('libtorrent',
 			sources = source_list,
 			language='c++',

configure.ac

@@ -123,6 +123,8 @@ AS_ECHO "Checking for boost libraries:"
 AX_BOOST_BASE([1.54])
 
 AX_CXX_COMPILE_STDCXX_11([noext], [mandatory])
+# Also put any flags added to CXX into CXXFLAGS
+CXXFLAGS="$CXXFLAGS $(echo "$CXX" | cut -d ' ' -f 2-)"
 
 AX_BOOST_SYSTEM()
 AS_IF([test -z "$BOOST_SYSTEM_LIB"],