Revision 5791

Switch BEGIN_TEXT over to use EV3P.
This allows for embedded TI calculator type entries which are converted to TeX.

e.g
$f = Formula("x^2/5");
BEGIN_TEXT
Print   formula inline `$f` or print it inline with `x^2/5`
END_TEXT
will now print typeset equations without needing to
use Context()->texStrings.
The code in ` ...   ` is parsed into a Formula and then printed using -> TeX