New file extension

[Eric Botcazou]

> Various Ada runtime library files are also .c under gcc/ada - in general,
> I'm not sure which .c files there are used as C, C++ or both, and which
> are used for host, target or both; that would require careful
> investigation for any renaming.

The C files directly under ada/ cannot be renamed since they are meant to be 
compiled by the C compiler; only the ones under ada/gcc-interface can.

-- 
Eric Botcazou