EGL_KHR_fence_sync: Add TODO to test for EGL_BAD_MATCH for attributes that don't match a sync type

Can't test this until there are more sync types with unique attributes.
EGL_KHR_fence_sync: eglCreateSyncKHR: Test passing an invalid sync type
EGL_KHR_fence_sync: drop an effectively untestable bit of the spec
util/egl: piglit_egl_bind_api: Add a missing newline to an error message
util/egl: Add a checked version of eglGetProcAddress

The new piglit_egl_get_proc_address fails the test if eglGetProcAddress
returns NULL.
EGL_KHR_fence_sync: Use piglit_egl_get_proc_address to get extension functions
EGL_KHR_fence_sync: Add TODO for multi-display test
util/egl: Add piglit_egl_get_default_display()

This function gets the default display for given platform.
EGL_KHR_fence_sync: Fix build

For the extension function pointers, the test used the same names as the
function prototypes in eglext.h. This collision broke the build. Fix the
build by changing prefix of function pointers from 'egl' to 'pegl'.
EGL_KHR_fence_sync: Factor out display initialization

Factor it into new function init_display().
EGL_KHR_fence_sync: Refactor context creation

Factor it to new function init_context().
EGL_KHR_fence_sync: Add func log_info()
EGL_KHR_fence_sync: Add subtest eglCreateSyncKHR_with_display_bound_in_other_thread
EGL_KHR_fence_sync: Add test eglCreateSyncKHR_wrong_display_same_thread