Regroup vtbl definitions to one translation unit (#1167)

Move function declarations to a new header file, with relevant existing
documentation.

Signed-off-by: Marco Antognini <marco.antognini@arm.com>

test_conformance/math_brute_force/unary.cpp

@@ -13,7 +13,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 //
+
 #include "function_list.h"
+#include "test_functions.h"
 #include "utility.h"
 
 #include <string.h>
@@ -22,12 +24,6 @@
 #include <sys/time.h>
 #endif
 
-int TestFunc_Float_Float(const Func *f, MTdata, bool relaxedMode);
-int TestFunc_Double_Double(const Func *f, MTdata, bool relaxedMode);
-
-extern const vtbl _unary = { "unary", TestFunc_Float_Float,
-                             TestFunc_Double_Double };
-
 static int BuildKernel(const char *name, int vectorSize, cl_uint kernel_count,
                        cl_kernel *k, cl_program *p, bool relaxedMode)
 {