Add conformance tests for cl_khr_extended_versioning (#548)

Tests that the new queries work, and that what they return is consistent with
the information returned by the string-based queries.

Signed-off-by: Einar Hov <einar.hov@arm.com>

test_conformance/compiler/test_compiler_defines_for_extensions.cpp

@@ -63,6 +63,7 @@ const char *known_extensions[] = {
     "cl_khr_priority_hints",
     "cl_khr_throttle_hints",
     "cl_khr_spirv_no_integer_wrap_decoration",
+    "cl_khr_extended_versioning",
 };
 
 size_t num_known_extensions = sizeof(known_extensions)/sizeof(char*);