Before this commit, the template compiler would guess the next block id
that will be generated when compiling the body of a tcall. This is
correct IF there are not nested t-call, but otherwise wrong, because the
next block id could be mixed up: the first t-call would save the next
block id (let's say n), then the inner t-call would also save the same
block id (so, n), will then generate its own block (n+1), then the outer
t-call would use the block n index instead of n+1
The best fix, in my opinion, is to make sure we get the next block var
name, so we do not have to guess. To do that, each compile block type
function needs to properly return the information.
closes#1267
t-out automatically escaped content when it is a string not marked
with the `markup` function
t-out renders the raw content if it is a Block, or if it has been marked
with the `markup` funtion.
t-esc has been kept since it is safe and is optimized to render text nodes.
all t-raw calls are in fact the same as t-out.