title: `set_major_locator` removes x-ticks (and labels) from previous subplots?
body: <p>I ran into this strange problem with using <code>set_major_locator()</code>, when using subplots which have different x-axis limits. A minimal example:</p>
  
  <pre><code>import matplotlib.pyplot as pl
  import matplotlib.dates as mdates
  from datetime import datetime
  
  h24 = mdates.HourLocator(interval=24)
  fmt = mdates.DateFormatter('%d-%m %H:%M')
  
  start1 = datetime(year=2016, month=7, day=7, hour=0)
  end1   = datetime(year=2016, month=7, day=9, hour=0)
  
  start2 = datetime(year=2016, month=9, day=30, hour=0)
  end2   = datetime(year=2016, month=10, day=2, hour=0)
  
  start3 = datetime(year=2016, month=5, day=8,  hour=0)
  end3   = datetime(year=2016, month=5, day=10, hour=0)
  
  pl.figure(figsize=(9,3))
  
  ax=pl.subplot(131)
  ax.set_xlim(start1, end1)
  ax.xaxis.set_major_locator(h24)
  ax.xaxis.set_major_formatter(fmt)
  
  ax=pl.subplot(132)
  ax.set_xlim(start2, end2)
  ax.xaxis.set_major_locator(h24)
  ax.xaxis.set_major_formatter(fmt)
  
  ax=pl.subplot(133)
  ax.set_xlim(start3, end3)
  ax.xaxis.set_major_locator(h24)
  ax.xaxis.set_major_formatter(fmt)
  
  pl.tight_layout()
  </code></pre>
  
  <p>Which results in:</p>
  
  <p><a href="https://i.stack.imgur.com/g15Wl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/g15Wl.png" alt="enter image description here"></a></p>
  
  <p>If I set the x-limit of all sub-plots the same (using in this case <code>ax.set_xlim(start1, end1)</code> for all sub-plots) it works as expected:</p>
  
  <p><a href="https://i.stack.imgur.com/bPQQF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/bPQQF.png" alt="enter image description here"></a></p>
  
  <p>Also, leaving the different <code>set_xlim()</code>'s and removing the <code>set_major_locator()</code> and <code>set_major_formatter()</code> lines works (although I get unreadable x-labels in this case..):</p>
  
  <p><a href="https://i.stack.imgur.com/VnQ3j.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VnQ3j.png" alt="enter image description here"></a></p>
  
  <p>Am I making a silly mistake somewhere, or are the missing x-ticks and labels in my first example a bug in Matplotlib?</p>
  
  <p><em>p.s. Matplotlib 3.0.2, Python 3.7.2</em></p>