[Bug c/68499] Unclear STDC FP_CONTRACT behavior in non-standard modes

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68499

--- Comment #2 from joseph at codesourcery dot com <joseph at codesourcery dot 
com> ---
Unknown pragmas are diagnosed with -Wunknown-pragmas (part of -Wall).