vtable's beginning/end-of-table functions broken/fix

[marty hiatt]

vtable.el's functions `vtable-beginning-of-table` and `vtable-end-of-table` 
seem broken to me. when i try to use `vtable-revert-command` on a table in a 
buffer that contains other text, reverting or re-sorting it removes everything 
in the buffer apart from the table.

to fix it, it looks like the call to `text-property-search-backward` for the 
former or `text-property-search-forward` for the latter requires a third 
argument (PREDICATE) of `t` rather than nil.

from the docstring:
"Two special values of PREDICATE can also be used:
If PREDICATE is t, that means the value of PROPERTY must `equal' VALUE
to be considered a match.
If PREDICATE is nil (which is the default), the value of PROPERTY will
match if it is not `equal' to VALUE."

with PREDICATE set to nil, the beginning/end-of-table functions use `point-min` 
and `point-max instead.