Parser: no jnf for Apple

At least on AppleClang and also seen in flang source-code, we
just call the double variant of `jn` instead of using a specialized
call to `jnf`.

This might be less efficient than needed with Intel on Apple, but
I don't have a system to test this on at the moment and this is thus
a save bet for compile stability.

Source/Parser/wp_parser_y.h

@@ -247,7 +247,7 @@ wp_call_f2 (enum wp_f2_t type, T a, T b)
         amrex::Abort();
         return 0.0;
 #else
-#   ifdef AMREX_USE_FLOAT
+#   ifdef AMREX_USE_FLOAT && !defined(__APPLE__)
         return jnf(a, b);
 #   else
         return jn(a, b);