New value format framework installed.

The idea is that we will precompile formats to avoid parsing the
format everytime a cell is repainted.

Miguel.

1998-08-19  Miguel de Icaza  <miguel@nuclecu.unam.mx>

	* src/format.c (format_value): The new entry point for formating
	values.  This takes a Value instead of a float.
	NULL is never returned from format_value now: if there is a format
	error, then value_string is used to display it.

	(format_compile): This routine should always return, it cant fail,
	in the worst * case it should just downgrade to simplistic formatting.

	(format_destroy): This routine is invoked when the last user of
	the format is gone (ie, refcount has reached zero) just before the
	StyleFormat structure is actually released.  resources allocated
	in format_compile should be disposed here