compiling patiencediff_c extension produce warnings

[Alexander Belchenko]

using official bzr-1.2.tar.gz I have this:

$ python setup.py build_ext
running build_ext
...
building 'bzrlib._patiencediff_c' extension
gcc -pthread -fno-strict-aliasing -DNDEBUG -O3 -march=i586 -mcpu=c3 -fPIC -I/usr/include/python2.4 -c 
bzrlib/_patiencediff_c.c -o build/temp.linux-i686-2.4/bzrlib/_patiencediff_c.o
In file included from /usr/include/python2.4/Python.h:8,
                  from bzrlib/_patiencediff_c.c:28:
/usr/include/python2.4/pyconfig.h:851:1: warning: "_POSIX_C_SOURCE" redefined
In file included from /usr/include/stdlib.h:25,
                  from bzrlib/_patiencediff_c.c:26:
/usr/include/features.h:190:1: warning: this is the location of the previous definition
gcc -pthread -shared build/temp.linux-i686-2.4/bzrlib/_patiencediff_c.o -o 
build/lib.linux-i686-2.4/bzrlib/_patiencediff_c.so