[xliff-tools] C-format annotations

[Bruno Haible]

1.4.1.4.2. C-format

<x> seems to be a more suitable placeholder than <it>: it does not require
a pos="open" attribute.

Unsolved question: How does this deal with reordering (in C, the POSIX
"%2$d" syntax)?

Also it makes it impossible to replace %d with %Id - an option needed by Farsi
translators.

How does this relate to <context context-type="numparams"> ?

Bruno