Support the profiles "constrained_baseline" and "high" for libopenh264
version >= 1.8, support "constrained_baseline" and "main" for earlier
version.

If option not supported with current version, convert to constrained
baseline with a warning for users.
Reviewed-by: Martin Storsjö <martin@martin.st>
Signed-off-by: Linjie Fu <linjie.fu@intel.com>