* mu4e: applied Michael Strey's patch for the date in citations

  What was going wrong?

  Using the function `mu4e-view-message-text',
  mu4e~draft-cite-original created a temporary buffer. Based on this
  buffer the function message-cite-original-without-signature,
  borrowed from Gnus, had to extract the date for the citation
  line. The problem was, that this function depends on a standardized
  date in ISO format whilst mu4e-view-message-text formatted the date
  according to the setting of mu4e-view-date-format.

  This patch hopefully solves this problem by setting
  mu4e-view-date-format in function mu4e~draft-cite-original.