templatefuncs: do not stringify result of if*() expression
Returning a generator means that the result is a byte string. I can't find
any reason to make the "if" condition lazy since it is evaluated anyway
when {if()} has to be evaluated. So let's simply make if*() return an input
expression unmodified.
ERROR: FIXME: This is a known failure of filelog.size for data starting with \1\n
OK.