- Security: close cross site scripting vulnerability in draft, compose

  - Security: close cross site scripting vulnerability in draft, compose
    and mailto functionality [CVE-2006-6142].
  - Security: work around an issue in Internet Explorer that would guess
    the mime type of a file based on contents, not Content-Type header.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@11968 7612ce4b-ef26-0410-bec9-ea0150e637f0