Check for correct format args count

[elegaanz]

• Check that the number of format arguments matches the one in the source string.
• Check that the same arguments are used in source strings and translations in compile_i18n?

[trinity-1686a]

Thinking about it, I wonder if compile_i18n and maybe other macros shouldn't actually be functions called from build.rs. They are not actually generating any code in the end executable and are just here for there side effects

[elegaanz]

The problem is that they need to be "called" after the .pot have been updated by the various i18n!/t! calls, but build.rs can only run before the crate itself is compiled.