readline: link in libtinfo to provide missing symbols

This is a working fix of the issue described [here](https://github.com/ContinuumIO/anaconda-issues/issues/42#issuecomment-39054576) by @kbg.  I have
almost posted a similarly long text myself, but a last minute google
search saved the day.

So, yeah, conda's build of readline is broken because of missing
`libtinfo` dependency which is re-injected to
`lib-dynload/readline.so`, probably by a patch.  I've fixed this
missing dependency for myself with a recipe in this PR and after a bit
of trial and error, I've come up with `build.sh` that built python 2.7.6
that was binary-compatible with conda's one from a clean tarball:

```
$ cat build.sh
./configure --prefix=$PREFIX --enable-shared --enable-ipv6 --enable-unicode=ucs4 \
    CPPFLAGS=-I$PREFIX/include LDFLAGS="-L$PREFIX/lib -Wl,-rpath=$PREFIX/lib" \
    && make -j$(getconf _NPROCESSORS_ONLN) \
    && LD_LIBRARY_PATH=$PREFIX/lib make install

```

Have used that since January without any issues, but not sure if it
works on other Linux flavours, so feel free to drop this PR and
reimplement it as you see fit.