Rename C files to .c in GCC source

[Eli Zaretskii]

> Date: Sat, 31 Jan 2015 01:55:29 +0000
> From: Jonathan Wakely <jwakely.gcc@gmail.com>
> Cc: Andrew Pinski <pinskia@gmail.com>, "gcc@gcc.gnu.org" <gcc@gcc.gnu.org>, Jonny Grant <jg@jguk.org>
> 
> These files are only compiled by GCC's own build system, with GCC's
> own makefiles, so we know we invoke the C++ compiler and so the
> language isn't inferred from the file extension, and so we aren't
> relying on case-sensitive file systems.

That is true for building GCC.  But what about editors and other
development tools?  They _will_ be affected.