Duplicate columns in DataFrame do not show up in DataFrame.itertuples
#### Code Sample, a copy-pastable example if possible

```python
>>> import pandas
>>> df = pandas.read_csv('test.csv')
>>> df
   A  A.1  B
0  1    2  3
>>> df.columns
Index(['A', 'A.1', 'B'], dtype='object')
>>> for row in df.itertuples(index=False):
...     print(row)
... 
Pandas(A=1, _1=2, B=3)
```
#### Problem description

The row should show up as `Pandas(A=1, A.1=2, B=3)` OR start supporting `mangle_dupe_cols=False` to overwrite duplicate columns.

#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit: None
python: 3.5.2.final.0
python-bits: 64
OS: Darwin
OS-release: 16.3.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.19.0
nose: None
pip: 9.0.1
setuptools: 30.3.0
Cython: None
numpy: 1.11.2
scipy: None
statsmodels: None
xarray: None
IPython: None
sphinx: None
patsy: None
dateutil: 2.5.3
pytz: 2016.7
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: None
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: None
pymysql: None
psycopg2: 2.6.2 (dt dec pq3 ext lo64)
jinja2: None
boto: 2.45.0
pandas_datareader: None

</details>
