[htmltmpl] TMPL_IF truth vs definition

[Tugrul G. <tu...@ga...>]

	Even though I read the documentation for HTML::Template at some point,
I had gotten into the habit of using TMPL_IF in the sense of if a
variable is defined instead of if it is true. Now 99% of the time this
just happens to work, as most defined things are also considered to be
true. But that 1% needs to be dealt with.

	I realize I could do this with H::T::Expr, but I don't want to go that
far (and it would require changing a lot of templates ;). And I could
start evaluating the defined condition in the code and exporting
booleans, but that triggers the valid warning in the documentation about
that.

	And I feel that ifdefined is fundamentally simple enough (almost
simpler than if true since its almost not even logic) that it should be
included.

	Now that I've lobbied for my cause :), I know a patch is generally a
big help in getting it passed. The question I have is how to proceed:

	1) Add a flag to switch TMPL_IF to the alternate behaviour (if defined
vs if true)
	2) Add another tag TMPL_IFDEF or similar.

	Tugrul Galatali