#I FORMAT
---------
The #I command has the following format:

#I <pattern> <x> <y> <rotate> <flip> <delay>

Any prefix of fields that includes a pattern name is acceptable, with defaults
taken to be backward compatible with old format.

<pattern> is a pattern name (described below).
<x> and <y> are integers representing horizontal and vertical offset.
<rotate> is an integer that specifies the number of times the pattern is rotated
         90 degrees clockwise around the origin.  Any value (positive or 
         negative) is acceptable, as all are taken mod 4 (true mod, not "%").
<flip> is a multiplier (1 or -1) for the y coordinate that specifies a flip 
         about the x-axis.  Other integers are accepted and silently mapped 
         to 1.
<delay> is an integer specifying the number of generations to perform before 
         loading the pattern (negative values have same effect as 0).

Note that all of the transformations applied to an included pattern are taken 
relative to the pattern that includes it.

Pattern Names
-------------
A pattern name takes one of the following three forms:

<file>         --   include whole file <file> (like old format)
<file>:<name>  --   include pattern block <name> in <file> 
:<name>        --   include pattern block <name> in current file 

(Note that <file>: is not allowed.)

Pattern Blocks
--------------
A pattern block is a pattern given in any acceptable format between a line
containing "#B <name>" and another line containing "#E".  Pattern blocks
are skipped when including a whole file.  

(Note that pattern blocks *cannot* be nested.)