Finding python library on Ubuntu 14.04 64bit

On Ubuntu 14.04, libpython must be search for in default paths, otherwise the architecture (`x86_64-linux`) is not taken in consideration.

```
find /usr/lib* -name "libpython*"
/usr/lib/python2.7/config-x86_64-linux-gnu/libpython2.7-pic.a
/usr/lib/python2.7/config-x86_64-linux-gnu/libpython2.7.a
/usr/lib/python2.7/config-x86_64-linux-gnu/libpython2.7.so
/usr/lib/python3.4/config-3.4m-x86_64-linux-gnu/libpython3.4m.so
/usr/lib/python3.4/config-3.4m-x86_64-linux-gnu/libpython3.4.so
/usr/lib/x86_64-linux-gnu/libpython2.7.so.1
/usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0
/usr/lib/x86_64-linux-gnu/libpython2.7.a
/usr/lib/x86_64-linux-gnu/libpython3.4m.so.1.0
/usr/lib/x86_64-linux-gnu/libpython3.4m.so.1
/usr/lib/x86_64-linux-gnu/libpython2.7.so
/usr/lib/libreoffice/program/libpythonloaderlo.so
```