lib/kernel: set -fno-math-errno & -std=c11
lib/kernel: set -fno-math-errno & -std=c11

The kernel library is always compiled with Clang,
so we can set the C standard to 11.

-fmath-errno (default) does not make sense with
pocl's kernel library.

pocl/pocl,franz/pocl,Oblomov/pocl,franz/pocl,franz/pocl,pocl/pocl,Oblomov/pocl,pocl/pocl,franz/pocl,Oblomov/pocl,Oblomov/pocl,franz/pocl,pocl/pocl,pocl/pocl,Oblomov/pocl