test: ignore deprecated-declarations for GCC >= 6.x

test: ignore deprecated-declarations for GCC >= 6.x

In libva 2.0 the VAProfileH264Baseline declaration has been
deprecated.

In the test/Makefile.am, we use -Wall -Werror so all warnings
are treated as errors.  For GCC < 6.x, deprecated-declarations
are not flagged as warnings, thus don't break compilation.
However, GCC >= 6.x treats deprecated-declarations as warnings
and therefore breaks compilation.

Ignore deprecated-declarations with the -Wno-deprecated-declarations
compiler flag for now.

Fixes #219

Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>