RFC: Moving C to its own directory

[Richard Kenner]

    The point is that currently we look for po/config-lang.in,
    intl/config-lang.in, fixinc/config-lang.in, etc. (waste of time, and
    could theoretically give false positives), and then we have to add
    whatever the file is for C.

I'm not sure I follow your point, but I agree that the C front end
should be in its own directory: I just think it should be gcc/c, not
gcc/lang/c or gcc/fe/c.