Broken Basemap rotpole projection

Nessuno ha ancora preso questa issue.

Initally posted by a mistake to matplotlib/matplotlib
https://github.com/matplotlib/matplotlib/issues/9541
Here seems to be more relevant..

### Bug report

**Bug summary**

Basemap can't plot rotated-pole maps that cross rotated-grid's 0-th meridian

**Code for reproduction**
Here is a simple code that produce two maps for non-rotated grid (zero-rotation).
One does not cross Greenwich meridian another one does.

```python
# Paste your code here
#
#
#!/usr/bin/python
import matplotlib as mpl
mpl.use('AGG')

import matplotlib.pyplot as plt
import numpy as np
from mpl_toolkits.basemap import Basemap
import os

figname="okay.png"
fig = plt.figure()
bmap = Basemap(projection='rotpole',
llcrnrx=0, urcrnry=15,
urcrnrx=25, llcrnry=-15,
lon_0 = 0,
o_lon_p = 0.,
o_lat_p = 90.,
resolution='c')

bmap.drawmapboundary(fill_color='aqua')
bmap.fillcontinents(color='coral',lake_color='aqua')
bmap.drawcoastlines(linewidth=0.5)
bmap.drawparallels(np.arange(-20,20,10.))
bmap.drawmeridians(np.arange(-40,40,10.))

mpl.pyplot.savefig(figname)

figname="broken.png"
fig.clf()

bmap = Basemap(projection='rotpole',
llcrnrx=-25, urcrnry=15,
urcrnrx=25, llcrnry=-15,
lon_0 = 0,
o_lon_p = 0.,
o_lat_p = 90.,
resolution='c')

bmap.drawmapboundary(fill_color='aqua')
bmap.fillcontinents(color='coral',lake_color='aqua')
bmap.drawcoastlines(linewidth=0.5)
bmap.drawparallels(np.arange(-20,20,10.))
bmap.drawmeridians(np.arange(-40,40,10.))

mpl.pyplot.savefig(figname)

```

**Actual outcome**
Here are two maps.. The second one is obviously broken.

**Matplotlib version**
* Operating system: Python 2.7.1, python-matplotlib 1.5.1-1ubuntu1
* Matplotlib version: 1.5.1-1ubuntu1
* Python version: 2.7.1

Default Ubuntu 16.04.3 LTS installation

Inizia eseguendo lo script di riproduzione fornito e confrontando le due mappe generate. Analizza la gestione da parte di Basemap della proiezione rotpole per i limiti che attraversano il meridiano zero della griglia ruotata; il lavoro è completato quando entrambi i casi visualizzano correttamente i confini della mappa, le coste, i continenti, i paralleli e i meridiani.

Scritto dal modello di indicizzazione a partire dal testo della issue.