[fdo] new Microsoft Outlook mime type for freedesktop.org.xml

[Joshua Julin]

Hello developers,

I noticed that no mime type for Microsoft Outlook is in the
freedesktop.org.xml file.

Adding the following to freedesktop.org.xml will correcly identify my
*.pst files:

  <mime-type type="application/vnd.ms-outlook">
    <comment>Microsoft Outlook</comment>
    <glob pattern="*.pst"/>
    <magic priority="50">
      <match value="0x4e444221" type="little32" offset="0"/>
    </magic>
  </mime-type>

I don't know if this magic number works for all pst files; it just works
for mine.
Does anyone know the correct way to identify Outlook files?

Thanks for the help,
Joshua Julin