-Wformat-diag: floating-point or floating point?

[Martin Sebor]

The GCC coding style says to use "floating-point" as an adjective
rather than "floating point."  After enhancing the -Wformat-diag
checker to detect this I found a bunch of uses of the latter, such
as in:

   gcc/c/c-decl.c:10944
   gcc/c/c-parser.c:9423, 9446, 9450, etc.
   gcc/convert.c:418, 422
   gcc/cp/call.c:5070
   gcc/cp/cvt.c:886

Before I fix them all and adjust the tests, I want to make sure
we really want to follow this rule.  The C standard uses both
interchangeably.  With just one exception, the C++ standard uses
the hyphenated form.

Thanks
Martin