For GL tests (those built by CMakeLists.gl.txt), if USE_WAFFLE is enabled
then freeglut is replaced with glut_waffle.

For GLES1 and GLES2 tests, glut_waffle is now required.
Reviewed-by: Pauli Nieminen <pauli.nieminen@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>

Nearly all CMakeLists.gl.txt contained the following:
    include_directories(${GLUT_INCLUDE_DIR})
    link_libraries(${GLUT_glut_LIBRARY})

This patch relocates them to cmake/target_api/gl/CMakeLists.txt.
Reviewed-by: Pauli Nieminen <pauli.nieminen@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>

Add two new CMakeLists, /cmake/target_api/{gl,gles2}/CMakeLists.txt, each
of which builds Piglit with its respective API. (Of course,
gles2/CMakeLists.txt adds no targets because Piglit does not yet support
building with GLES2.)

The toplevel CMakeLists no longer adds subdirectory /tests; that is now
the responsiblity of the API-specific CMakeLists.

Note: This belongs to a series that adds GLES2 support to Piglit.
Signed-off-by: Chad Versace <chad.versace@intel.com>