[ZPT] changing the order of operations

[Jamie Heilman]

Chris Withers wrote:
> Jamie Heilman wrote:
> 
> >If the omit-tag expression evaluates to true, or is empty, the tag is
>                                                 ^^^^^^^^^^^
> This second bit is extremely bogus, wrong and just plain unpythonic :-(((((

Meh.  TAL isn't python.  The common case is the quickest to type,
thats a good thing, the only incongruity is that 'default' is false
for tal:omit-tag and true for tal:condition.  While thats odd, its not
particularly debilitating, whereas the speed issues with TAL are.