gcc: cleaning up top level config

[Robert Dewar]

For reference, the coding convention for Ada units in the GNAT sources
is no use of tabs and no trailing spaces, and these rules are enforced
by the GNAT compiler when it compiles its own units (this is one of the
effects of the -gnatg flag required for compiling units of the compiler).
Our rule is that there should be nothing "invisible" in sources, and
sources that look the same must be the same.

I would have preferred to enforce the same rules for C units in GNAT, but
Richard Kenner insisted that gcc coding rules require the use of tabs :-(