Find a way to allow c:if work with partial state saving enabled

This one is difficult to solve but I still think it is possible.

It was explored trying to solve MYFACES-2428, and it seems ri is trying to do something about it too on:

https://javaserverfaces.dev.java.net/issues/show_bug.cgi?id=1408

and

https://javaserverfaces.dev.java.net/issues/show_bug.cgi?id=1313

One strategy to solve this one is this:

1. Mark the parent component containing c:if to not save it partially.
2. Do not execute c:if on postback and partial state saving enabled.

In theory, the parent component should be restored fully from saved state.

Note that things like:

<c:if>....
<p>Some markup</p>
<c:if>

is just invalid. It is expected that c:if only contains components with state.