Add notes on TheDraw .TDF font format.

src/syncdraw/TDF_FORMAT

+<dig dig dig>
+It does use pascal strings...
+struct TDHeader {
+   /* Pascal string [23] - TheDraw Font signature */
+   /* There may be unknown data after this string instead of a 23 char string */
+   unsigned char    sig_len;
+   char             sig[23];
+   /* Pascal string [16] - Font name */
+   unsigned char    name_len;
+   char             name[16];
+   unsigned char    font_type;      /* 0=outline,
+   									 * 1=Block (mono)
+									 * 2=Block(colour)
+									 */
+   unsigned char    font_spaces;   /* Spaces between each letter */
+   unsigned short   font_data_len;    /* Total bytes in the font data... file
+   									   * size is font_data_len+233 
+									   */
+   unsigned short   chartable[94];   /* Offsets to character start from end of
+   									  * header ie:
+									  * fseek(file, chartable[x]+233, SEEK_SET);
+									  */
+};
+
+So basically:
+string[23]
+string[16]
+byte
+byte
+word
+word[94]
+
+Is the header... which is 233 bytes long.
+
+sizeof(struct TDHeader)==233;
+
+Now on to the font data...
+
+index into the chartable array is asc(char)-asc("!") ie: ! is the first char.
+The char data starts at file offset 233+chartable[char].
+
+At that position are two bytes, the X and Y extents in that order for that char.
+Following that is a series of font data **rows** each row is terminated by an 
+ASCII 10 (\x0a).  The character data is terminated by an ASCII NULL (\x00)
+This is true for all three font types.  The meaning of each char however varies
+as follows:
+0) Outline fonts:
+   Each char *MUST* be between 'A' and 'Q'.  Any other char is translated as an
+   empty space.
+   A: Horiz. Line #1
+   B: Horiz. Line #2
+   C: Vertical Line #1
+   D: Vertical Line #2
+   E: Top-left corner #1
+   F: Top-right corner #1
+   G: Top-left corner #2
+   H: Top-right corner #2
+   I: Bottom-left corner #1
+   J: Bottom-right corner #1
+   K: Bottom-left corner #2
+   L: Bottom-right corner #2
+   M: Left-facing tee
+   N: Right-facing tee
+   O: UNKNOWN
+   P: UNKNOWN
+   Q: UNKNOWN
+   I note that the Up-facing and Down-facing tees are absent and speculate that
+   they are O and P but have no hard evidence of this.  If anyone has a TD
+   outline font editor, I would be happy to get a sample of a font using them.
+   I also suspect that Q is a blank space.
+1) Block fonts
+   Each char is the ASCII value that should be displayed at this point.
+2) Block colour fonts
+   Each char has an attribute, in char, attribute format.  The newlines and NULL
+   terminator do NOT have an attribute byte... be carefull.