Displays the table of file name extensions and the associated
 Content-Type and Content-Transfer-Encoding that is employed when
 files of each type are attached to an outgoing message using the
 ADD command.

 Like the CONTENT_TYPE table, the FILE_TYPES are defined by
 built-in entries, followed by system-wide entries, followed by
 local user-defined entries.  File type definitions are found in
 the configuration file MIME$FILETYPES.DAT, which is found in
 the SYS$MANAGER: directory and in the user's SYS$LOGIN: directory.

1  –  Examples

 MIME> sho file
 Known File Types:
 Extension: HTML, Content-Type: text/html, Encoding: 7bit/8bit

 This example shows "Known File Types" for MIME as defined in the
 MIME program, and any others configured in the MIME$FILETYPES.DAT
 file. When composing a MIME message, the ADD command uses these
 corresponding settings when given only the file name and extension,
 (or file type), for example:

 MIME> add myfile.html

 This would add the file "myfile.html" with the content type set to
 "text/html" and an encoding of "7bit/8bit".

2  –  MIME$FILETYPES.DAT

 The FILE_TYPES table is constructed from program built-in types
 and is read from the simple comma separated list in the
 MIME$FILETYPES.DAT configuration files, (if they exist).

 System-wide FILE_TYPES are specified by the file
 SYS$MANAGER:MIME$FILETYPES.DAT and can be supplemented with
 additional entries found in the SYS$LOGIN:MIME$FILETYPES.DAT file.

 The table is constructed beginning with the built-in types, then
 adding the system definitions from SYS$MANAGER:MIME$FILETYPES.DAT,
 and ending with data from the SYS$LOGIN:MIME$FILETYPES.DAT file.

 The entries are displayed in order of the most recently defined
 (LIFO) entries. In the case of duplicate entries, the first entry
 is used. This allows a user to customize their own environment while
 the system manager defines a default system or site environment
 for all users.

3  –  Example MIME$FILETYPES.DAT

 These following file and its two entries define how to add .JPG and
 .JPEG files with a "Content-Type" of image/jpg, and an "Encoding" of
 Base64.

 # MIME File Type Information File
 #
 #       These entries are used when adding MIME attachments.
 #
 # '#' is a comment delimiter
 #
 # Example:
 #
 #       File Extension:    Content-Type:   Encoding:
 #       ---------------    -------------   ---------
 #
 #       jpg,               image/jpg,      Base64
 #       jpeg,              image/jpeg,     Base64
 #
 # Other examples can be copied from Netscape's MIME.TYPES
 #
 #
 # DECsound
 aud , audio/x-aud , base64
 #
 # WAV
         wav,            audio/x-wav,    Base64
 #
 # JPG
 jpg, image/jpg, Base64
 jpeg, image/jpeg, Base64
 #
 #
 # CDA Viewer
 ps, application/ps, Base64
 ddif, application/ddif, Base64
 #
 # PDF
 pdf, application/pdf, Base64
 #
 # For PC applications we don't have
 # ---------------------------------
 doc, application/msword, Base64
 xls, application/xls,    Base64
 ppt, application/ppt,    Base64