How to clear unknown pragma warning for OpenMP?

[Jeffrey Walton]

>> g++ -DNDEBUG -g2 -O3 -Wall -fPIC -march=native -pipe -c rw.cpp
>> rw.cpp:130:0: warning: ignoring #pragma omp parallel [-Wunknown-pragmas]
>>   #pragma omp parallel sections if(CRYPTOPP_RW_USE_OMP)
>>  ^
>
> Pretty ugly, but if you want the OpenMP directives to be dependent on
> whether OpenMP support is actually enabled you could do:
>
> #if _OPENMP
> #pragma omp section
> #endif
>

Yeah, we kind of looked at that and rejected it some time ago.

What do you think about some #defines to make them disappear? Can a
define be crafted that captures multiple lexemes or tokens?

Jeff