Reserved plugin letters
-----------------------

Used in @x24R@ constructs where x is:

D - date plugin.
M - Mark 'n lard plugin.
S - Sesame Street plugin.
U - uptime plugin.


Macros
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Used in @x constructs where x is:

B - Newline (think Break line)
F - First name
L - Last name
N - Full name
V - Version in the form x.y.z

The name variants are only available if htag is passed a message with
headers like "To: Simon Huggins <huggie@earth.li>".


Magic Reformatting
------------------

This isn't supported yet but I think it's what I want.  I just need to be
able to match nested constructs but I think there is a module for this.
Hmm.  Need more CFT.
Used in @x24@ constructs where x is:

CENTER	- Center over line width
RIGHT	- Right align
LEFT	- Left align with padding

Without a following length the operations are done over the line width.