title: Getting "Could not find function xmlCheckVersion in library libxml2. Is libxml2 installed?" when installing lxml through pip
body: <p>I'm getting an error <code>Could not find function xmlCheckVersion in library libxml2. Is libxml2 installed?</code> when trying to install lxml through pip.</p>
  <pre><code>  c:\users\f\appdata\local\temp\xmlXPathInitqjzysz.c(1) : fatal error C1083: Cannot open include file: 'libxml/xpath.h': No such file or directory
    *********************************************************************************
    Could not find function xmlCheckVersion in library libxml2. Is libxml2 installed?
    *********************************************************************************
    error: command 'C:\\Users\\f\\AppData\\Local\\Programs\\Common\\Microsoft\\Visual C++ for Python\\9.0\\VC\\Bin\\cl.exe' failed with exit status 2
  </code></pre>
  <p>I don't find any libxml2 dev packages to install via pip.</p>
  <p>Using Python 2.7 and Python 3.x on x86 in a virtualenv under Windows 10.</p>